Add integration test support for volume mounts

libcnb-test/src/container_config.rs

@@ -1,4 +1,5 @@
 use std::collections::{HashMap, HashSet};
+use std::path::{Path, PathBuf};
 
 /// Config used when starting a container.
 ///
@@ -31,6 +32,7 @@ pub struct ContainerConfig {
     pub(crate) command: Option<Vec<String>>,
     pub(crate) env: HashMap<String, String>,
     pub(crate) exposed_ports: HashSet<u16>,
+    pub(crate) volumes: HashMap<PathBuf, PathBuf>,
 }
 
 impl ContainerConfig {
@@ -169,6 +171,37 @@ impl ContainerConfig {
         self
     }
 
+    /// Mounts a named volume `source` into the container `destination`. Useful for integration
+    /// tests that depend on persistent storage shared between container executions.
+    ///
+    /// See: [Docker CLI, Mount Volume](https://docs.docker.com/reference/cli/docker/container/run/#volume)
+    ///
+    /// # Example
+    /// ```no_run
+    /// use libcnb_test::{BuildConfig, ContainerConfig, TestRunner};
+    /// use std::path::PathBuf;
+    ///
+    /// TestRunner::default().build(
+    ///     BuildConfig::new("heroku/builder:22", "tests/fixtures/app"),
+    ///     |context| {
+    ///         // ...
+    ///         context.start_container(
+    ///             ContainerConfig::new().volume(PathBuf::from("/shared/cache"), PathBuf::from("/workspace/cache")),
+    ///             |container| {
+    ///                 // ...
+    ///             },
+    ///         );
+    ///     },
+    /// );
+    /// ```
+    pub fn volume<P: AsRef<Path>>(&mut self, source: P, destination: P) -> &mut Self {
+        self.volumes.insert(
+            source.as_ref().to_path_buf(),
+            destination.as_ref().to_path_buf(),
+        );
+        self
+    }
+
     /// Adds or updates multiple environment variable mappings for the container.
     ///
     /// # Example

libcnb-test/src/docker.rs

@@ -1,4 +1,5 @@
 use std::collections::{BTreeMap, BTreeSet};
+use std::path::PathBuf;
 use std::process::Command;
 
 /// Represents a `docker run` command.
@@ -9,6 +10,7 @@ pub(crate) struct DockerRunCommand {
     detach: bool,
     entrypoint: Option<String>,
     env: BTreeMap<String, String>,
+    volumes: BTreeMap<PathBuf, PathBuf>,
     exposed_ports: BTreeSet<u16>,
     image_name: String,
     platform: Option<String>,
@@ -23,6 +25,7 @@ impl DockerRunCommand {
             detach: false,
             entrypoint: None,
             env: BTreeMap::new(),
+            volumes: BTreeMap::new(),
             exposed_ports: BTreeSet::new(),
             image_name: image_name.into(),
             platform: None,
@@ -53,6 +56,15 @@ impl DockerRunCommand {
         self
     }
 
+    pub(crate) fn volume(
+        &mut self,
+        source: impl Into<PathBuf>,
+        destination: impl Into<PathBuf>,
+    ) -> &mut Self {
+        self.volumes.insert(source.into(), destination.into());
+        self
+    }
+
     pub(crate) fn expose_port(&mut self, port: u16) -> &mut Self {
         self.exposed_ports.insert(port);
         self
@@ -98,6 +110,17 @@ impl From<DockerRunCommand> for Command {
             command.args(["--publish", &format!("127.0.0.1::{port}")]);
         }
 
+        for (source, destination) in &docker_run_command.volumes {
+            command.args([
+                "--volume",
+                &format!(
+                    "{}:{}",
+                    source.to_string_lossy(),
+                    destination.to_string_lossy()
+                ),
+            ]);
+        }
+
         command.arg(docker_run_command.image_name);
 
         if let Some(container_command) = docker_run_command.command {
@@ -311,6 +334,7 @@ mod tests {
         docker_run_command.entrypoint("/usr/bin/bash");
         docker_run_command.env("BAR", "2");
         docker_run_command.env("FOO", "1");
+        docker_run_command.volume(PathBuf::from("./test-cache"), PathBuf::from("/cache"));
         docker_run_command.expose_port(12345);
         docker_run_command.expose_port(55555);
         docker_run_command.platform("linux/amd64");
@@ -337,6 +361,8 @@ mod tests {
                 "127.0.0.1::12345",
                 "--publish",
                 "127.0.0.1::55555",
+                "--volume",
+                "./test-cache:/cache",
                 "my-image",
                 "echo",
                 "hello",

libcnb-test/src/test_context.rs

@@ -108,6 +108,10 @@ impl<'a> TestContext<'a> {
             docker_run_command.env(key, value);
         });
 
+        config.volumes.iter().for_each(|(source, destination)| {
+            docker_run_command.volume(source, destination);
+        });
+
         config.exposed_ports.iter().for_each(|port| {
             docker_run_command.expose_port(*port);
         });