diff --git a/.JuliaFormatter.toml b/.JuliaFormatter.toml
new file mode 100644
index 0000000..ffd961f
--- /dev/null
+++ b/.JuliaFormatter.toml
@@ -0,0 +1,10 @@
+# Configuration file for JuliaFormatter.jl
+# For more information, see: https://domluna.github.io/JuliaFormatter.jl/stable/config/
+
+verbose = true
+format_markdown = true
+remove_extra_newlines = true
+always_for_in = true
+conditional_to_if = true
+always_use_return = true
+format_docstrings = true
diff --git a/.github/workflows/FormatCheck.yml b/.github/workflows/FormatCheck.yml
new file mode 100644
index 0000000..8f47bb2
--- /dev/null
+++ b/.github/workflows/FormatCheck.yml
@@ -0,0 +1,31 @@
+name: FormatCheck
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    types: [opened, synchronize, reopened]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: julia-actions/setup-julia@latest
+        with:
+          version: '1'
+      - uses: actions/checkout@v1
+      - name: Format check
+        shell: julia --color=yes {0}
+        run: |
+          using Pkg
+          # If you update the version, also update the style guide docs.
+          Pkg.add(PackageSpec(name="JuliaFormatter", version="1"))
+          using JuliaFormatter
+          format("src", verbose=true)
+          format("test", verbose=true)
+          out = String(read(Cmd(`git diff`)))
+          if isempty(out)
+              exit(0)
+          end
+          @error "Some files have not been formatted!"
+          write(stdout, out)
+          exit(1)
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 37e48fb..8f8a2cc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,4 +6,5 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [0.1.0]
-- Initial release 
+
+  - Initial release
diff --git a/README.md b/README.md
index 516b066..d1c880e 100644
--- a/README.md
+++ b/README.md
@@ -8,6 +8,7 @@ Currently, JSON is used for serialization, and only optimization
 solvers and constraint programming solvers are supported.
 
 ## API
+
 The main API is `solve` which takes a JSON request or Julia dictionary
 and a solver and returns a response.
 
@@ -17,12 +18,12 @@ using SolverAPI
 import HiGHS
 
 tiny_min = Dict(
-        "version" => "0.1",
-        "sense" => "min",
-        "variables" => ["x"],
-        "constraints" => [["==", "x", 1], ["Int", "x"]],
-        "objectives" => ["x"],
-    )
+    "version" => "0.1",
+    "sense" => "min",
+    "variables" => ["x"],
+    "constraints" => [["==", "x", 1], ["Int", "x"]],
+    "objectives" => ["x"],
+)
 
 solve(tiny_min, HiGHS.Optimizer())
 ```
@@ -30,7 +31,9 @@ solve(tiny_min, HiGHS.Optimizer())
 ## Format
 
 ### Request
+
 Request format example:
+
 ```json
 {
   "version": "0.1",
@@ -58,29 +61,35 @@ Request format example:
   }
 }
 ```
+
 Required fields:
-- `version`: [String] The version of the API that is used.
-- `options`: [Array] Options, such as the time limit, if the
-  model should be printed, or general solver attributes. For a
-  complete list, please refer to the documentation of the solver.
-- `sense`: [String] One of `feas`, `min`, or `max`
-- `variables`: [Array] A list of variables that are used in the model.
-- `constraints`: [Array] A list of constraints. Each constraint
-  contains an operation and a set of arguments, such as `["==", "x", 1]`.
-- `objectives`: [Array] The objective. 
+
+  - `version`: [String] The version of the API that is used.
+  - `options`: [Array] Options, such as the time limit, if the
+    model should be printed, or general solver attributes. For a
+    complete list, please refer to the documentation of the solver.
+  - `sense`: [String] One of `feas`, `min`, or `max`
+  - `variables`: [Array] A list of variables that are used in the model.
+  - `constraints`: [Array] A list of constraints. Each constraint
+    contains an operation and a set of arguments, such as `["==", "x", 1]`.
+  - `objectives`: [Array] The objective.
 
 #### Options
+
 We always support the following options:
-- `silent`: [Bool] Controls if the solver prints any logs.
-- `time_limit_sec`: [Float64] Limits the total time expended. The optimization
-  returns a `TIME_LIMIT` status.
-- `print_only`: [Bool] If set to true the model will only be printed
-  and not solved.
-- `print_format`: [String] If and how the model should be
-  printed. Currently supported formats: default, LaTex, MOF, LP, MPS, NL.
+
+  - `silent`: [Bool] Controls if the solver prints any logs.
+  - `time_limit_sec`: [Float64] Limits the total time expended. The optimization
+    returns a `TIME_LIMIT` status.
+  - `print_only`: [Bool] If set to true the model will only be printed
+    and not solved.
+  - `print_format`: [String] If and how the model should be
+    printed. Currently supported formats: MOI, LaTeX, MOF, LP, MPS, NL.
 
 ### Response
+
 Response format examples:
+
 ```json
 {
   "version": "0.1",
@@ -88,10 +97,10 @@ Response format examples:
     {
       "objective_value": 0.0,
       "primal_status": "FEASIBLE_POINT",
-      "sol_names": [
+      "names": [
         "\"x\""
       ],
-      "sol_values": [
+      "values": [
         1
       ]
     }
@@ -99,7 +108,9 @@ Response format examples:
   "termination_status": "OPTIMAL"
 }
 ```
+
 Example with a model error:
+
 ```json
 {
   "version": "0.1",
@@ -114,6 +125,7 @@ Example with a model error:
 ```
 
 Example with printing and no solving:
+
 ```json
 {
   "model_string": "{\"name\":\"MathOptFormat Model\",\"version\":{\"major\":1,\"minor\":4},\"variables\":[{\"name\":\"x\"}],\"objective\":{\"sense\":\"min\",\"function\":{\"type\":\"Variable\",\"name\":\"x\"}},\"constraints\":[{\"name\":\"c1\",\"function\":{\"type\":\"ScalarAffineFunction\",\"terms\":[{\"coefficient\":1.0,\"variable\":\"x\"}],\"constant\":0.0},\"set\":{\"type\":\"EqualTo\",\"value\":1.0}},{\"function\":{\"type\":\"Variable\",\"name\":\"x\"},\"set\":{\"type\":\"Integer\"}}]}",
@@ -123,16 +135,16 @@ Example with printing and no solving:
 ```
 
 Required fields:
-- `version`: [String] The version of the API that is used.
-- `termination_status`: [String] The MOI termination status.
+
+  - `version`: [String] The version of the API that is used.
+  - `termination_status`: [String] The MOI termination status.
 
 Optional fields:
-- `results`: [Array] The results array. Depending on
-  the optimization none, one, or multiple results will be
-  present. Each result will contain multiple fields describing the
-  solution, such as `objective_value`, `primal_status`,
-  `sol_names`, and `sol_values`.
-- `errors`: [Array] None, one, or multiple errors that were present.
-- `model_string`: [String] If requested via `print_format` the model
-as a string. 
 
+  - `results`: [Array] The results array. Zero, one, or multiple
+    results will be present. Each result will contain multiple fields
+    describing the solution, such as `objective_value`, `primal_status`,
+    `names`, and `values`.
+  - `errors`: [Array] None, one, or multiple errors that were present.
+  - `model_string`: [String] If requested via `print_format` the model
+    as a string.
diff --git a/src/SolverAPI.jl b/src/SolverAPI.jl
index 6b026ef..164fabf 100644
--- a/src/SolverAPI.jl
+++ b/src/SolverAPI.jl
@@ -3,11 +3,9 @@
 
 This module provides an interface to solve optimization problems.
 
-Exports `solve`, `print_model`, `response`, `serialize`, and
-`deserialize`.
+Exports `solve`, `print_model`, `response`, `serialize`, and `deserialize`.
 
-Our format is based on JSON. For examples, please see `tests/inputs`
-and `tests/outputs`.
+Our format is based on JSON. For examples, see `tests/inputs` and `tests/outputs`.
 """
 module SolverAPI
 
@@ -29,23 +27,18 @@ An `@enum` of possible errors types.
 
 ## Values
 
-- `InvalidFormat`: The request is syntactically incorrect. Expected
-  fields might be missing or of the wrong type.
-
-- `InvalidModel`: The model is semantically incorrect. For example, an
-  unknown `sense` was provided.
-
-- `Unsupported`: Some unsupported feature was used. That includes
-  using unsupported attributes for a solver or specifying an
-  unsupported solver.
-
-- `NotAllowed`: An operation is supported but cannot be applied in the
-  current state of the model
-
-- `Domain`: A domain-specific, internal error occurred. For example, a
-  function cannot be converted to either linear or quadratic form.
-
-- `Other`: An error that does not fit in any of the above categories.
+  - `InvalidFormat`: The request is syntactically incorrect. Expected
+    fields might be missing or of the wrong type.
+  - `InvalidModel`: The model is semantically incorrect. For example, an
+    unknown `sense` was provided.
+  - `Unsupported`: Some unsupported feature was used. That includes
+    using unsupported attributes for a solver or specifying an
+    unsupported solver.
+  - `NotAllowed`: An operation is supported but cannot be applied in the
+    current state of the model
+  - `Domain`: A domain-specific, internal error occurred. For example, a
+    function cannot be converted to either linear or quadratic form.
+  - `Other`: An error that does not fit in any of the above categories.
 """
 @enum ErrorType InvalidFormat InvalidModel Unsupported NotAllowed Domain Other
 
@@ -60,18 +53,20 @@ end
 Return a response
 
 ## Args
-- `request::SolverAPI.Request`: [optionally] The request that was received.
-- `model::MOI.ModelLike`: [optionally] The model that was solved.
+
+  - `request::SolverAPI.Request`: [optionally] The request that was received.
+  - `model::MOI.ModelLike`: [optionally] The model that was solved.
 
 ## Keyword Args
-- `version::String`: The version of the API.
-- `termination_status::MOI.TerminationStatus`: The termination status of the solver.
-- `errors::SolverAPI.Error`: A vector of `Error`s.
+
+  - `version::String`: The version of the API.
+  - `termination_status::MOI.TerminationStatus`: The termination status of the solver.
+  - `errors::SolverAPI.Error`: A vector of `Error`s.
 """
 function response(;
-    version="0.1",
-    termination_status=MOI.OTHER_ERROR,
-    errors::Vector{Error}=Error[],
+    version = "0.1",
+    termination_status = MOI.OTHER_ERROR,
+    errors::Vector{Error} = Error[],
 )
     pairs = Pair{String,Any}["version"=>version, "termination_status"=>termination_status]
     if !isempty(errors)
@@ -79,8 +74,8 @@ function response(;
     end
     return Dict(pairs)
 end
-response(error::Error; kw...) = response(; errors=[error], kw...)
-function response(json::Request, model::MOI.ModelLike; version="0.1", kw...)
+response(error::Error; kw...) = response(; errors = [error], kw...)
+function response(json::Request, model::MOI.ModelLike; version = "0.1", kw...)
     res = Dict{String,Any}()
 
     res["version"] = version
@@ -101,9 +96,9 @@ function response(json::Request, model::MOI.ModelLike; version="0.1", kw...)
 
     result_count = MOI.get(model, MOI.ResultCount())
 
-    results = [Dict{String,Any}() for _ = 1:result_count]
+    results = [Dict{String,Any}() for _ in 1:result_count]
 
-    for idx = 1:result_count
+    for idx in 1:result_count
         results[idx]["primal_status"] = MOI.get(model, MOI.PrimalStatus(idx))
 
         if status in (MOI.OPTIMAL, MOI.LOCALLY_SOLVED)
@@ -128,16 +123,15 @@ end
 """
     serialize([io], response::Response)
 
-Serialize the `response`. 
+Serialize the `response`.
 
 ## Args
-- `io::IO`: An optional IO stream to write to. If not provided, a
-  `Vector{UInt8}` is returned.
-- `response`: A `SolverAPI.Response` to serialize.
+
+  - `io::IO`: An optional IO stream to write to. If not provided, a
+    `Vector{UInt8}` is returned.
+  - `response`: A `SolverAPI.Response` to serialize.
 """
-function serialize(response::Response)
-    return Vector{UInt8}(JSON3.write(response))
-end
+serialize(response::Response) = Vector{UInt8}(JSON3.write(response))
 serialize(io::IO, response::Response) = JSON3.write(io, response)
 
 """
@@ -147,9 +141,7 @@ serialize(io::IO, response::Response) = JSON3.write(io, response)
 Deserialize `body` to an `Request`. Returns an instances that can be
 used with `solve` or `print_model`.
 """
-function deserialize(body::Vector{UInt8})
-    return JSON3.read(body)
-end
+deserialize(body::Vector{UInt8}) = JSON3.read(body)
 deserialize(body::String) = deserialize(Vector{UInt8}(body))
 
 """
@@ -160,11 +152,11 @@ gracefully and included in `Response`.
 
 ## Args
 
-- `fn`: [Optionally] A function to call before solving the problem. This is useful
-  for setting up custom solver options. The function is called with
-  the `MOI.ModelLike` model and should return `Nothing`.
-- `request`: A `SolverAPI.Request` specifying the optimization problem.
-- `solver`: A `MOI.AbstractOptimizer` to use to solve the problem.
+  - `fn`: [Optionally] A function to call before solving the problem. This is useful
+    for setting up custom solver options. The function is called with
+    the `MOI.ModelLike` model and should return `Nothing`.
+  - `request`: A `SolverAPI.Request` specifying the optimization problem.
+  - `solver`: A `MOI.AbstractOptimizer` to use to solve the problem.
 """
 function solve(fn, json::Request, solver::MOI.AbstractOptimizer)
     errors = validate(json)
@@ -212,51 +204,56 @@ solve(request::Dict, solver::MOI.AbstractOptimizer) =
     print_model(model::MOI.ModelLike, format::String)::String
 
 Print the `model`. `format` options (case-insensitive) are:
-- `default`
-- `LaTeX`
-- `MOF`
-- `LP`
-- `MPS`
-- `NL`
+
+  - `MOI` (MathOptInterface default printout)
+  - `LaTeX` (MathOptInterface default LaTeX printout)
+  - `MOF` (MathOptFormat file)
+  - `LP` (LP file)
+  - `MPS` (MPS file)
+  - `NL` (NL file)
 """
 function print_model(model::MOI.ModelLike, format::String)
-    format = lowercase(format)
-    if format == "default" || format == "latex"
-        mime = MIME(format == "latex" ? "text/latex" : "text/plain")
-        options =
-            MOI.Utilities._PrintOptions(mime; simplify_coefficients=true, print_types=false)
+    format_lower = lowercase(format)
+    if format_lower == "moi" || format_lower == "latex"
+        mime = MIME(format_lower == "latex" ? "text/latex" : "text/plain")
+        options = MOI.Utilities._PrintOptions(
+            mime;
+            simplify_coefficients = true,
+            print_types = false,
+        )
         return sprint() do io
-            MOI.Utilities._print_model(io, options, model)
+            return MOI.Utilities._print_model(io, options, model)
         end
-    elseif format == "latex"
+    elseif format_lower == "latex"
         # NOTE: there are options for latex_formulation, e.g. don't print MOI function/set types
         # https://jump.dev/MathOptInterface.jl/dev/submodules/Utilities/reference/#MathOptInterface.Utilities.latex_formulation
         return sprint(print, MOI.Utilities.latex_formulation(model))
-    elseif format == "mof"
-        options = (; format=MOI.FileFormats.FORMAT_MOF, print_compact=true)
-    elseif format == "lp"
-        options = (; format=MOI.FileFormats.FORMAT_LP)
-    elseif format == "mps"
-        options = (; format=MOI.FileFormats.FORMAT_MPS)
-    elseif format == "nl"
-        options = (; format=MOI.FileFormats.FORMAT_NL)
+    elseif format_lower == "mof"
+        options = (; format = MOI.FileFormats.FORMAT_MOF, print_compact = true)
+    elseif format_lower == "lp"
+        options = (; format = MOI.FileFormats.FORMAT_LP)
+    elseif format_lower == "mps"
+        options = (; format = MOI.FileFormats.FORMAT_MPS)
+    elseif format_lower == "nl"
+        options = (; format = MOI.FileFormats.FORMAT_NL)
     else
-        throw(Error(Unsupported, "File type $format not supported."))
+        throw(Error(Unsupported, "File type \"$format\" not supported."))
     end
     dest = MOI.FileFormats.Model(; options...)
     MOI.copy_to(dest, model)
     return sprint(write, dest)
 end
-function print_model(request::Request; T=Float64)
+function print_model(request::Request; T = Float64)
     errors = validate(request)
-
     if length(errors) > 0
         throw(CompositeException(errors))
     end
 
     options = get(() -> Dict{String,Any}(), request, :options)
-    format = get(options, :print_format, "default")
+    # Default to MOI format.
+    format = get(options, :print_format, "MOI")
 
+    # TODO cleanup/refactor solver_info logic.
     use_indicator = T == Float64
     solver_info = Dict{Symbol,Any}(:use_indicator => use_indicator)
     model = MOI.Utilities.Model{T}()
@@ -266,76 +263,57 @@ function print_model(request::Request; T=Float64)
 end
 print_model(request::Dict) = print_model(JSON3.read(JSON3.write(request)))
 
-
 # Internal
 # ========================================================================================
 
 function validate(json::Request)#::Vector{Error}
     out = Error[]
+    # Helper for adding errors
+    _err(msg::String) = push!(out, Error(InvalidFormat, msg))
     valid_shape = true
 
     # Syntax.
     for k in [:version, :sense, :variables, :constraints, :objectives]
         if !haskey(json, k)
             valid_shape = false
-            push!(out, Error(InvalidFormat, "Missing required field `$(k)`."))
+            _err("Missing required field `$(k)`.")
         end
     end
 
     # If the shape is not valid we can't continue.
-    if !valid_shape
-        return out
-    end
+    valid_shape || return out
 
     if !isa(json.version, String)
-        push!(out, Error(InvalidFormat, "Invalid `version` field. Must be a string."))
+        _err("Invalid `version` field. Must be a string.")
     end
 
     if json.version != "0.1"
-        push!(
-            out,
-            Error(
-                InvalidFormat,
-                """Invalid version `$(repr(json.version))`. Only `"0.1"` is supported.""",
-            ),
-        )
+        _err("Invalid version `$(repr(json.version))`. Only `\"0.1\"` is supported.")
     end
 
     if haskey(json, :options) && !isa(json.options, JSON3.Object)
-        push!(out, Error(InvalidFormat, "Invalid `options` field. Must be an object."))
+        _err("Invalid `options` field. Must be an object.")
     end
 
     for k in [:variables, :constraints, :objectives]
         if !isa(json[k], JSON3.Array)
-            push!(out, Error(InvalidFormat, "Invalid `$(k)` field. Must be an array."))
+            _err("Invalid `$(k)` field. Must be an array.")
         end
     end
 
     if any(si -> !isa(si, String), json.variables)
-        push!(out, Error(InvalidFormat, "Variables must be of type `String`."))
+        _err("Variables must be of type `String`.")
     end
 
     # Semantics.
     if !in(json.sense, ["feas", "min", "max"])
-        push!(
-            out,
-            Error(
-                InvalidModel,
-                "Invalid `sense` field. Must be one of `feas`, `min`, or `max`.",
-            ),
-        )
+        _err("Invalid `sense` field. Must be one of `feas`, `min`, or `max`.")
     end
 
     if haskey(json, :options)
         for (T, k) in [(String, :print_format), (Number, :time_limit_sec)]
             if haskey(json.options, k) && !isa(json.options[k], T)
-                push!(
-                    out,
-                    Error(
-                        InvalidFormat,
-                        "Invalid `options.$(k)` field. Must be of type `$(T)`.",
-                    ),
-                )
+                _err("Invalid `options.$(k)` field. Must be of type `$(T)`.")
             end
         end
 
@@ -344,13 +322,7 @@ function validate(json::Request)#::Vector{Error}
                 val = json.options[k]
                 # We allow `0` and `1` for convenience.
                 if !isa(val, Bool) && val isa Number && val != 0 && val != 1
-                    push!(
-                        out,
-                        Error(
-                            InvalidFormat,
-                            "Invalid `options.$(k)` field. Must be a boolean.",
-                        ),
-                    )
+                    _err("Invalid `options.$(k)` field. Must be a boolean.")
                 end
             end
         end
@@ -358,29 +330,20 @@ function validate(json::Request)#::Vector{Error}
 
     if json.sense == "feas"
         if !isempty(json.objectives)
-            push!(
-                out,
-                Error(InvalidModel, "Objectives must be empty when `sense` is `feas`."),
-            )
+            _err("Objectives must be empty when `sense` is `feas`.")
         end
     else
         if length(json.objectives) != 1
-            push!(out, Error(InvalidModel, "Only a single objective is supported."))
+            _err("Only a single objective is supported.")
         end
     end
 
     for con in json.constraints
         if first(con) == "range"
             if length(con) != 5
-                push!(
-                    out,
-                    Error(InvalidModel, "The `range` constraint expects 4 arguments."),
-                )
+                _err("The `range` constraint expects 4 arguments.")
             elseif con[4] != 1
-                push!(
-                    out,
-                    Error(InvalidModel, "The `range` constraint expects a step size of 1."),
-                )
+                _err("The `range` constraint expects a step size of 1.")
             end
         end
     end
@@ -388,7 +351,6 @@ function validate(json::Request)#::Vector{Error}
     return out
 end
 
-
 function initialize(json::Request, solver::MOI.AbstractOptimizer)#::Tuple{Type, Dict{Symbol, Any}, MOI.ModelLike}
     solver_info = Dict{Symbol,Any}()
 
@@ -403,7 +365,7 @@ function initialize(json::Request, solver::MOI.AbstractOptimizer)#::Tuple{Type,
         solver_info[:use_indicator] = true
     end
 
-    model = MOI.instantiate(() -> solver; with_cache_type=T, with_bridge_type=T)
+    model = MOI.instantiate(() -> solver; with_cache_type = T, with_bridge_type = T)
 
     for (key, val) in options
         if key in [:solver, :print_format, :print_only]
@@ -524,17 +486,6 @@ function canonicalize_SNF(::Type{T}, f) where {T<:Real}
     return f
 end
 
-# TODO(cdc) experiment more:
-# function canonicalize_SNF(::Type{T}, f) where {T <: Real}
-#     try
-#         f = convert(MOI.ScalarQuadraticFunction{T}, f)
-#         try
-#             f = convert(MOI.ScalarAffineFunction{T}, f)
-#         catch end
-#     catch end
-#     return f
-# end
-
 function add_obj!(
     ::Type{T},
     model::MOI.ModelLike,
@@ -570,12 +521,8 @@ function add_cons!(
 
     function _check_v_type(v)
         if !(v isa MOI.VariableIndex)
-            throw(
-                Error(
-                    InvalidModel,
-                    "Variable $v must be of type MOI.VariableIndex, not $(typeof(v)).",
-                ),
-            )
+            msg = "Variable $v must be of type MOI.VariableIndex, not $(typeof(v))."
+            throw(Error(InvalidModel, msg))
         end
     end
 
@@ -583,7 +530,9 @@ function add_cons!(
         for i in eachindex(a)
             i == 1 && continue
             if a[i] isa Bool
-                a[i] || push!(out, Error(InvalidModel, "Model is infeasible."))
+                if !a[i]
+                    throw(Error(InvalidModel, "Model is infeasible."))
+                end
             else
                 add_cons!(T, model, a[i], vars_map, solver_info)
             end
@@ -611,8 +560,9 @@ function add_cons!(
     elseif head == "range"
         v = json_to_snf(a[5], vars_map)
 
-        (a[2] isa Int && a[3] isa Int) ||
+        if !(a[2] isa Int && a[3] isa Int)
             throw(Error(InvalidModel, "The `range` constraint expects integer bounds."))
+        end
         _check_v_type(v)
 
         MOI.add_constraint(model, v, MOI.Integer())
@@ -620,34 +570,29 @@ function add_cons!(
     elseif head == "implies" && solver_info[:use_indicator]
         # TODO maybe just check if model supports indicator constraints
         # use an MOI indicator constraint
-        length(a) == 3 ||
+        if length(a) != 3
             throw(Error(InvalidModel, "The `implies` constraint expects 2 arguments."))
+        end
         f = json_to_snf(a[2], vars_map)
         g = json_to_snf(a[3], vars_map)
-        (f.head == :(==) && length(f.args) == 2) || throw(
-            Error(
-                InvalidModel,
-                "The first argument of the `implies` constraint expects to be converted to an equality SNF with 2 arguments.",
-            ),
-        )
+        if !(f.head == :(==) && length(f.args) == 2)
+            msg = "The first argument of the `implies` constraint expects to be converted to an equality SNF with 2 arguments."
+            throw(Error(InvalidModel, msg))
+        end
 
         v, b = f.args
         _check_v_type(v)
-        (b == 1 || b == 0) || throw(
-            Error(
-                InvalidModel,
-                "The second argument of the derived equality SNF from the `implies` constraint expects a binary variable.",
-            ),
-        )
+        if b != 1 && b != 0
+            msg = "The second argument of the derived equality SNF from the `implies` constraint expects a binary variable."
+            throw(Error(InvalidModel, msg))
+        end
 
         A = (b == 1) ? MOI.ACTIVATE_ON_ONE : MOI.ACTIVATE_ON_ZERO
         S1 = get(ineq_to_moi, g.head, nothing)
-        (!isnothing(S1) && length(g.args) == 2) || throw(
-            Error(
-                InvalidModel,
-                "The second argument of the `implies` constraint expects to be converted to an (in)equality SNF with 2 arguments.",
-            ),
-        )
+        if isnothing(S1) || length(g.args) != 2
+            msg = "The second argument of the `implies` constraint expects to be converted to an (in)equality SNF with 2 arguments."
+            throw(Error(InvalidModel, msg))
+        end
 
         h = shift_terms(T, g.args)
         vaf = MOI.Utilities.operate(vcat, T, v, h)
@@ -663,12 +608,8 @@ function add_cons!(
             g = shift_terms(T, f.args)
             s = S(zero(T))
             if !MOI.supports_constraint(model, typeof(g), typeof(s))
-                throw(
-                    Error(
-                        Unsupported,
-                        "Constraint $g in $s isn't supported by this solver.",
-                    ),
-                )
+                msg = "Constraint $g in $s isn't supported by this solver."
+                throw(Error(Unsupported, msg))
             end
             ci = MOI.Utilities.normalize_and_add_constraint(model, g, s)
         end
@@ -679,7 +620,7 @@ end
 ineq_to_moi = Dict(:<= => MOI.LessThan, :>= => MOI.GreaterThan, :(==) => MOI.EqualTo)
 
 function shift_terms(::Type{T}, args::Vector) where {T<:Real}
-    @assert length(args) == 2 # This should never happen. 
+    @assert length(args) == 2 # This should never happen.
     g1 = canonicalize_SNF(T, args[1])
     g2 = canonicalize_SNF(T, args[2])
     return MOI.Utilities.operate(-, T, g1, g2)
diff --git a/test/inputs/cons_is_not_arr.json b/test/inputs/cons_is_not_arr.json
index da0db3a..456fce1 100644
--- a/test/inputs/cons_is_not_arr.json
+++ b/test/inputs/cons_is_not_arr.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":["x"],"constraints":"==","objectives":[],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/feas_range.json b/test/inputs/feas_range.json
index 4ffb36a..fb5b943 100644
--- a/test/inputs/feas_range.json
+++ b/test/inputs/feas_range.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":["x"],"constraints":[["range",9, 9, 1, "x"],["Float","x"]],"objectives":[],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/feas_with_obj.json b/test/inputs/feas_with_obj.json
index 9e35e03..70759f9 100644
--- a/test/inputs/feas_with_obj.json
+++ b/test/inputs/feas_with_obj.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"objectives":["x"],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/incorrect_range_num_params.json b/test/inputs/incorrect_range_num_params.json
index 258f048..0d7bf99 100644
--- a/test/inputs/incorrect_range_num_params.json
+++ b/test/inputs/incorrect_range_num_params.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":["x"],"constraints":[["range", 9, 9, "x"],["Int","x"]],"objectives":[],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/incorrect_range_step_not_1.json b/test/inputs/incorrect_range_step_not_1.json
index e8c79f4..88dbf36 100644
--- a/test/inputs/incorrect_range_step_not_1.json
+++ b/test/inputs/incorrect_range_step_not_1.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":["x"],"constraints":[["range",9, 9, 2, "x"],["Int","x"]],"objectives":[],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/incorrect_solver.json b/test/inputs/incorrect_solver.json
index 94b6d64..730b3f9 100644
--- a/test/inputs/incorrect_solver.json
+++ b/test/inputs/incorrect_solver.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"objectives":[],"options":{"solver":"Cplex"}}
-
diff --git a/test/inputs/min_no_obj.json b/test/inputs/min_no_obj.json
index d8f1c37..7f9c38c 100644
--- a/test/inputs/min_no_obj.json
+++ b/test/inputs/min_no_obj.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"min","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"objectives":[],"options":{"time_limit_sec":60,"solver":"HiGHS","silent":0,"print_format":"MOF"}}
-
diff --git a/test/inputs/min_range.json b/test/inputs/min_range.json
index 743a512..487c0dc 100644
--- a/test/inputs/min_range.json
+++ b/test/inputs/min_range.json
@@ -1,2 +1 @@
-{"version":"0.1","sense":"min","variables":["x"],"constraints":[["range",0,9,1,"x"],["Int","x"]],"objectives":["x"],"options":{"time_limit_sec":60,"solver":"HiGHS","silent":0,"print_format":"MOF"}}
-
+{"version":"0.1","sense":"min","variables":["x"],"constraints":[["range",0,9,1,"x"],["Int","x"]],"objectives":["x"],"options":{"time_limit_sec":60,"solver":"HiGHS","silent":0,"print_format":"MOI"}}
diff --git a/test/inputs/missing_cons.json b/test/inputs/missing_cons.json
index ba46190..89b7338 100644
--- a/test/inputs/missing_cons.json
+++ b/test/inputs/missing_cons.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":["x"],"objectives":[],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/missing_objs.json b/test/inputs/missing_objs.json
index 1ef0617..8ccf681 100644
--- a/test/inputs/missing_objs.json
+++ b/test/inputs/missing_objs.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/missing_sense.json b/test/inputs/missing_sense.json
index 1bf3ee2..fcf11ba 100644
--- a/test/inputs/missing_sense.json
+++ b/test/inputs/missing_sense.json
@@ -1,2 +1 @@
 {"version":"0.1","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"objectives":[],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/missing_vars.json b/test/inputs/missing_vars.json
index cbac8fc..b182b50 100644
--- a/test/inputs/missing_vars.json
+++ b/test/inputs/missing_vars.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","constraints":[["==","x",1],["Int","x"]],"objectives":[],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/missing_version.json b/test/inputs/missing_version.json
index cd0c8d3..f9241e7 100644
--- a/test/inputs/missing_version.json
+++ b/test/inputs/missing_version.json
@@ -1,2 +1 @@
 {"sense":"feas","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"objectives":[],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/n_queens.json b/test/inputs/n_queens.json
new file mode 100644
index 0000000..e77a8fc
--- /dev/null
+++ b/test/inputs/n_queens.json
@@ -0,0 +1 @@
+{"version":"0.1","sense":"feas","variables":["q_1","q_2","q_3","q_4"],"constraints":[["range",1,4,1,"q_1"],["range",1,4,1,"q_2"],["range",1,4,1,"q_3"],["range",1,4,1,"q_4"],["and",["and",["!=","q_1","q_2"],["!=",["abs",["-","q_1","q_2"]],1]],["and",["!=","q_1","q_3"],["!=",["abs",["-","q_1","q_3"]],2]],["and",["!=","q_1","q_4"],["!=",["abs",["-","q_1","q_4"]],3]],["and",["!=","q_2","q_3"],["!=",["abs",["-","q_2","q_3"]],1]],["and",["!=","q_2","q_4"],["!=",["abs",["-","q_2","q_4"]],2]],["and",["!=","q_3","q_4"],["!=",["abs",["-","q_3","q_4"]],1]]]],"objectives":[],"options":{"solver":"MiniZinc"}}
diff --git a/test/inputs/obj_len_greater_than_1.json b/test/inputs/obj_len_greater_than_1.json
index 89c9a52..1aae734 100644
--- a/test/inputs/obj_len_greater_than_1.json
+++ b/test/inputs/obj_len_greater_than_1.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"min","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"objectives":["x","x+1"],"options":{"time_limit_sec":60,"solver":"HiGHS","silent":0,"print_format":"MOF"}}
-
diff --git a/test/inputs/objs_is_not_arr.json b/test/inputs/objs_is_not_arr.json
index f075111..bcb8a11 100644
--- a/test/inputs/objs_is_not_arr.json
+++ b/test/inputs/objs_is_not_arr.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"objectives":"x","options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/simple_lp.json b/test/inputs/simple_lp.json
new file mode 100644
index 0000000..7ffd886
--- /dev/null
+++ b/test/inputs/simple_lp.json
@@ -0,0 +1 @@
+{"version":"0.1","sense":"min","variables":["x","y"],"constraints":[["and",["==",["+","x",["*",3,"y"]],1],[">=",["+","x","y"],1]],["and",["Int","x"],["Nonneg","x"]],["Int","y"]],"objectives":[["+",["*",2,"x"],"y"]],"options":{"solver":"HiGHS"}}
diff --git a/test/inputs/tiny_feas.json b/test/inputs/tiny_feas.json
index 893d910..d6d4877 100644
--- a/test/inputs/tiny_feas.json
+++ b/test/inputs/tiny_feas.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"objectives":[],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/tiny_infeas.json b/test/inputs/tiny_infeas.json
index b65c21f..92188e7 100644
--- a/test/inputs/tiny_infeas.json
+++ b/test/inputs/tiny_infeas.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":["x"],"constraints":[["range",10, 9, 1, "x"],["Float","x"]],"objectives":[],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/tiny_min.json b/test/inputs/tiny_min.json
index 2af457f..e21e7fe 100644
--- a/test/inputs/tiny_min.json
+++ b/test/inputs/tiny_min.json
@@ -1,2 +1 @@
-{"version":"0.1","sense":"min","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"objectives":["x"],"options":{"time_limit_sec":60,"solver":"HiGHS","silent":0,"print_format":"MOF"}}
-
+{"version":"0.1","sense":"min","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"objectives":["x"],"options":{"time_limit_sec":60,"solver":"HiGHS","silent":0,"print_format":"LaTeX"}}
diff --git a/test/inputs/unsupported_print_format.json b/test/inputs/unsupported_print_format.json
new file mode 100644
index 0000000..75ab80d
--- /dev/null
+++ b/test/inputs/unsupported_print_format.json
@@ -0,0 +1 @@
+{"version":"0.1","sense":"min","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"objectives":["x"],"options":{"time_limit_sec":60,"solver":"HiGHS","silent":0,"print_format":"What"}}
diff --git a/test/inputs/unsupported_sense.json b/test/inputs/unsupported_sense.json
index b4e932c..b69ed57 100644
--- a/test/inputs/unsupported_sense.json
+++ b/test/inputs/unsupported_sense.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feasibility","variables":["x"],"constraints":[["==","x",1],["Int","x"]],"objectives":["x"],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/vars_is_not_arr.json b/test/inputs/vars_is_not_arr.json
index 2794d4c..b14018c 100644
--- a/test/inputs/vars_is_not_arr.json
+++ b/test/inputs/vars_is_not_arr.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":"x","constraints":[["==","x",1],["Int","x"]],"objectives":[],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/inputs/vars_is_not_str.json b/test/inputs/vars_is_not_str.json
index bdb7f2f..7c5e765 100644
--- a/test/inputs/vars_is_not_str.json
+++ b/test/inputs/vars_is_not_str.json
@@ -1,2 +1 @@
 {"version":"0.1","sense":"feas","variables":[0],"constraints":[["==","x",1],["Int","x"]],"objectives":[],"options":{"solver":"MiniZinc"}}
-
diff --git a/test/outputs/min_range.json b/test/outputs/min_range.json
index d0f898c..d6144f8 100644
--- a/test/outputs/min_range.json
+++ b/test/outputs/min_range.json
@@ -1,2 +1 @@
-{"version":"0.1", "model_string":"{\"name\":\"MathOptFormat Model\",\"version\":{\"major\":1,\"minor\":4},\"variables\":[{\"name\":\"x\"}],\"objective\":{\"sense\":\"min\",\"function\":{\"type\":\"Variable\",\"name\":\"x\"}},\"constraints\":[{\"function\":{\"type\":\"Variable\",\"name\":\"x\"},\"set\":{\"type\":\"Interval\",\"lower\":0.0,\"upper\":9.0}},{\"function\":{\"type\":\"Variable\",\"name\":\"x\"},\"set\":{\"type\":\"Integer\"}}]}","termination_status":"OPTIMAL","results":[{"primal_status":"FEASIBLE_POINT", "names":["\"x\""],"values":[0.0],"objective_value":0.0}]}
-
+{"model_string":"Minimize: x\n\nSubject to:\n x ∈ [0, 9]\n x ∈ ℤ\n","termination_status":"OPTIMAL","results":[{"names":["\"x\""],"values":[0.0],"primal_status":"FEASIBLE_POINT","objective_value":0.0}],"version":"0.1"}
diff --git a/test/outputs/n_queens.json b/test/outputs/n_queens.json
new file mode 100644
index 0000000..03a3498
--- /dev/null
+++ b/test/outputs/n_queens.json
@@ -0,0 +1 @@
+{"termination_status":"OPTIMAL","results":[{"primal_status":"FEASIBLE_POINT","names":["\"q_1\"","\"q_2\"","\"q_3\"","\"q_4\""],"values":[2,4,1,3]}],"version":"0.1"}
diff --git a/test/outputs/simple_lp.json b/test/outputs/simple_lp.json
new file mode 100644
index 0000000..207c412
--- /dev/null
+++ b/test/outputs/simple_lp.json
@@ -0,0 +1 @@
+{"termination_status":"OPTIMAL","results":[{"primal_status":"FEASIBLE_POINT","names":["\"x\"","\"y\""],"values":[1.0,0.0],"objective_value":2.0}],"version":"0.1"}
diff --git a/test/outputs/tiny_feas.json b/test/outputs/tiny_feas.json
index c3371b1..bb3ac4f 100644
--- a/test/outputs/tiny_feas.json
+++ b/test/outputs/tiny_feas.json
@@ -1,3 +1 @@
 {"version":"0.1", "termination_status":"OPTIMAL","results":[{"primal_status": "FEASIBLE_POINT", "names":["\"x\""],"values":[1]}]}
-
-
diff --git a/test/outputs/tiny_infeas.json b/test/outputs/tiny_infeas.json
index 4f6ad5c..f68de06 100644
--- a/test/outputs/tiny_infeas.json
+++ b/test/outputs/tiny_infeas.json
@@ -1,2 +1 @@
 {"version":"0.1", "termination_status":"INFEASIBLE"}
-
diff --git a/test/outputs/tiny_min.json b/test/outputs/tiny_min.json
index 50361a1..1cbe96e 100644
--- a/test/outputs/tiny_min.json
+++ b/test/outputs/tiny_min.json
@@ -1,3 +1 @@
-{"version": "0.1", "model_string":"{\"name\":\"MathOptFormat Model\",\"version\":{\"major\":1,\"minor\":4},\"variables\":[{\"name\":\"x\"}],\"objective\":{\"sense\":\"min\",\"function\":{\"type\":\"Variable\",\"name\":\"x\"}},\"constraints\":[{\"name\":\"c1\",\"function\":{\"type\":\"ScalarAffineFunction\",\"terms\":[{\"coefficient\":1.0,\"variable\":\"x\"}],\"constant\":0.0},\"set\":{\"type\":\"EqualTo\",\"value\":1.0}},{\"function\":{\"type\":\"Variable\",\"name\":\"x\"},\"set\":{\"type\":\"Integer\"}}]}","termination_status":"OPTIMAL","results":[{"primal_status": "FEASIBLE_POINT", "names":["\"x\""],"values":[1.0],"objective_value":1.0}]}
-
-
+{"model_string":"$$ \\begin{aligned}\n\\min\\quad & x \\\\\n\\text{Subject to}\\\\\n & x = 1 \\\\\n & x \\in \\mathbb{Z} \\\\\n\\end{aligned} $$","termination_status":"OPTIMAL","results":[{"names":["\"x\""],"values":[1.0],"primal_status":"FEASIBLE_POINT","objective_value":1.0}],"version":"0.1"}
diff --git a/test/solve_tests.jl b/test/solve_tests.jl
index 88b11ec..860b892 100644
--- a/test/solve_tests.jl
+++ b/test/solve_tests.jl
@@ -10,11 +10,12 @@ export run_solve, read_json
 
 function _get_solver(solver_name::String)
     if solver_name == "MiniZinc"
-        solver = MiniZinc.Optimizer{Int}("chuffed")
+        return MiniZinc.Optimizer{Int}("chuffed")
+    elseif solver_name == "HiGHS"
+        return HiGHS.Optimizer()
     else
-        solver = HiGHS.Optimizer()
+        error("Solver $solver_name not supported.")
     end
-    return solver
 end
 
 function run_solve(input::String)
@@ -34,7 +35,15 @@ end # end of setup module.
     import JSON3
 
     # names of JSON files in inputs/ and outputs/ folders
-    json_names = ["feas_range", "min_range", "tiny_min", "tiny_feas", "tiny_infeas"]
+    json_names = [
+        "feas_range",
+        "min_range",
+        "tiny_min",
+        "tiny_feas",
+        "tiny_infeas",
+        "simple_lp",
+        "n_queens",
+    ]
 
     @testset "$j" for j in json_names
         input = read_json("inputs", j)
@@ -54,40 +63,42 @@ end
         :objectives => ["x"],
     )
 
-    for format in ["default", "latex", "mof", "lp", "mps", "nl"]
+    # test each format
+    for format in ["moi", "latex", "mof", "lp", "mps", "nl"]
         options = Dict(:print_format => format)
         @test print_model(Dict(tiny_min..., :options => options)) isa String
     end
-
 end
 
 @testitem "validate" setup = [SolverSetup] begin
     using SolverAPI: deserialize, validate
     import JSON3
 
-    # scenarios with incorrect format 
+    # scenarios with incorrect format
     format_err_json_names = [
+        # TODO fix: error not thrown for "unsupported_print_format"
+        # "unsupported_print_format",     # print format not supported
         "feas_with_obj",                # objective provided for a feasibility problem
         "min_no_obj",                   # no objective function specified for a minimization problem
-        "unsupported_sense",            # unsupported sense such as 'feasiblity' 
+        "unsupported_sense",            # unsupported sense such as 'feasiblity'
         "obj_len_greater_than_1",       # length of objective greater than 1
-        "incorrect_range_num_params",   # number of parameters not equal to 4 
+        "incorrect_range_num_params",   # number of parameters not equal to 4
         "incorrect_range_step_not_1",   # step not one in range definition
-        "vars_is_not_str",              # field variables is not a string 
-        "vars_is_not_arr",              # field variables is not an array 
-        "objs_is_not_arr",              # field objectives is not an array 
-        "cons_is_not_arr",              # field constraints is not an array 
-        "missing_vars",                 # missing field variables 
-        "missing_cons",                 # missing field constraints 
-        "missing_objs",                 # missing field objectives 
+        "vars_is_not_str",              # field variables is not a string
+        "vars_is_not_arr",              # field variables is not an array
+        "objs_is_not_arr",              # field objectives is not an array
+        "cons_is_not_arr",              # field constraints is not an array
+        "missing_vars",                 # missing field variables
+        "missing_cons",                 # missing field constraints
+        "missing_objs",                 # missing field objectives
         "missing_sense",                # missing field sense
-        "missing_version",              # missing field version 
+        "missing_version",              # missing field version
     ]
 
     @testset "$j" for j in format_err_json_names
         input = deserialize(read_json("inputs", j))
         errors = validate(input)
+        @test errors isa Vector{SolverAPI.Error}
         @test length(errors) >= 1
-        @test all(errors[i] isa SolverAPI.Error for i in eachindex(errors))
     end
 end