diff --git a/lib/cli.js b/lib/cli.js
index a4deb87d..fe49dfe9 100755
--- a/lib/cli.js
+++ b/lib/cli.js
@@ -1,111 +1,35 @@
 #!/usr/bin/env node
 "use strict";
 
-//console.dir(argv);
-
-//TODO: what to require?
 const csdl = require("odata-csdl");
 const lib = require("./csdl2openapi");
-const minimist = require("minimist");
 const fs = require("fs");
+const { parseArgs } = require("./cliParts");
 const { stringifyStream } = require("@discoveryjs/json-ext");
 
-var unknown = false;
-
-var argv = minimist(process.argv.slice(2), {
-  string: [
-    "basePath",
-    "description",
-    "host",
-    "keep",
-    "levels",
-    "openapi-version",
-    "scheme",
-    "target",
-    "title",
-  ],
-  boolean: ["diagram", "help", "pretty", "skipBatchPath", "used-schemas-only"],
-  alias: {
-    d: "diagram",
-    h: "help",
-    k: "keep",
-    o: "openapi-version",
-    p: "pretty",
-    t: "target",
-    u: "used-schemas-only",
-  },
-  default: {
-    levels: 4,
-    pretty: false,
-    skipBatchPath: false,
-  },
-  unknown: (arg) => {
-    if (arg.substring(0, 1) == "-") {
-      console.error("Unknown option: " + arg);
-      unknown = true;
-      return false;
-    }
-  },
-});
-
-if (unknown || argv._.length == 0 || argv.h) {
-  console.log(`Usage: odata-openapi3 <options> <source file>
-Options:
- --basePath              base path (default: /service-root)
- --description           default description if none is annotated
- -d, --diagram           include YUML diagram
- -h, --help              show this info
- --host                  host (default: localhost)
- -k, --keep              root resource to keep (can be specified multiple times with one name each)
- --levels                maximum number of path segments
- -o, --openapi-version   3.0.0 to 3.0.3 or 3.1.0 (default: 3.0.2)
- -p, --pretty            pretty-print JSON result
- --scheme                scheme (default: http)
- --skipBatchPath         skips the generation of the $batch path, (default: false)
- -t, --target            target file (default: source file basename + .openapi3.json)
- --title                 default title if none is annotated`);
-} else {
-  //TODO: further input parameters reserved for e.g. referenced CSDL documents
-  // for (var i = 0; i < argv._.length; i++) {
-  //     convert(argv._[i]);
-  // }
-  convert(argv._[0]);
-}
+const args = parseArgs(process.argv.slice(2));
+if (args.unknown)
+  args.unknown.map((arg) => console.error(`Unknown option: ${arg}`));
+if (args.usage) console.log(args.usage);
+else convert(args);
 
-function convert(source) {
-  if (!fs.existsSync(source)) {
-    console.error("Source file not found: " + source);
+function convert(args) {
+  if (!fs.existsSync(args.source)) {
+    console.error("Source file not found: " + args.source);
     return;
   }
 
-  const text = fs.readFileSync(source, "utf8");
+  const text = fs.readFileSync(args.source, "utf8");
   const json = text.startsWith("<") ? csdl.xml2json(text) : JSON.parse(text);
 
-  const target =
-    argv.target ||
-    (source.lastIndexOf(".") <= 0
-      ? source
-      : source.substring(0, source.lastIndexOf("."))) + ".openapi3.json";
-  console.log(target);
+  console.log(args.target);
 
   const messages = [];
 
-  const openapi = lib.csdl2openapi(json, {
-    scheme: argv.scheme,
-    host: argv.host,
-    basePath: argv.basePath,
-    diagram: argv.diagram,
-    maxLevels: Number(argv.levels),
-    openapiVersion: argv.o,
-    messages,
-    skipBatchPath: argv.skipBatchPath,
-    defaultTitle: argv.title,
-    defaultDescription: argv.description,
-    rootResourcesToKeep: Array.isArray(argv.keep) ? argv.keep : argv.keep? [argv.keep]: undefined,
-  });
+  const openapi = lib.csdl2openapi(json, { messages, ...args.options });
 
-  stringifyStream(openapi, null, argv.pretty ? 4 : 0).pipe(
-    fs.createWriteStream(target),
+  stringifyStream(openapi, null, args.options.pretty ? 4 : 0).pipe(
+    fs.createWriteStream(args.target),
   );
 
   if (messages.length > 0) console.dir(messages);
diff --git a/lib/cliParts.js b/lib/cliParts.js
new file mode 100644
index 00000000..931f2033
--- /dev/null
+++ b/lib/cliParts.js
@@ -0,0 +1,111 @@
+/**
+ * Parse command-line options
+ *
+ * Latest version: https://github.com/oasis-tcs/odata-openapi/blob/main/lib/cliOptions.js
+ */
+
+const minimist = require("minimist");
+
+module.exports = { parseArgs };
+
+function parseArgs(argv) {
+  const usage = `Usage: odata-openapi3 <options> <source file>
+  Options:
+   --basePath              base path (default: /service-root)
+   --description           default description if none is annotated
+   -d, --diagram           include YUML diagram
+   -h, --help              show this info
+   --host                  host (default: localhost)
+   -k, --keep              root resource to keep (can be specified multiple times with one name each)
+   --levels                maximum number of path segments
+   -o, --openapi-version   3.0.0 to 3.0.3 or 3.1.0 (default: 3.0.2)
+   -p, --pretty            pretty-print JSON result
+   --scheme                scheme (default: http)
+   --skipBatchPath         skips the generation of the $batch path, (default: false)
+   -t, --target            target file (default: source file basename + .openapi3.json)
+   --title                 default title if none is annotated`;
+  const unknown = [];
+
+  const args = minimist(argv, {
+    string: [
+      "basePath",
+      "description",
+      "host",
+      "keep",
+      "levels",
+      "openapi-version",
+      "scheme",
+      "target",
+      "title",
+    ],
+    boolean: ["diagram", "help", "pretty", "skipBatchPath"],
+    alias: {
+      d: "diagram",
+      h: "help",
+      k: "keep",
+      o: "openapi-version",
+      p: "pretty",
+      t: "target",
+    },
+    default: {
+      pretty: false,
+    },
+    unknown: (arg) => {
+      if (arg.substring(0, 1) == "-") {
+        unknown.push(arg);
+        return false;
+      }
+    },
+  });
+
+  if (unknown.length > 0 || args.help || args._.length !== 1)
+    return {
+      unknown,
+      usage,
+    };
+
+  const source = args._[0];
+  const target =
+    args.target ||
+    (source.lastIndexOf(".") > 0
+      ? source.substring(0, source.lastIndexOf("."))
+      : source) + ".openapi3.json";
+
+  const options = {};
+
+  for (const [name, value] of Object.entries(args)) {
+    if (name.length === 1) continue;
+    if (value === false) continue;
+    switch (name) {
+      case "description":
+        options.defaultDescription = value;
+        break;
+      case "keep":
+        if (Array.isArray(value)) options.rootResourcesToKeep = value;
+        else options.rootResourcesToKeep = [value];
+        break;
+      case "levels": {
+        const l = Number(value);
+        if (!isNaN(l)) options.maxLevels = l;
+        break;
+      }
+      case "openapi-version":
+        options.openapiVersion = value;
+        break;
+      case "target":
+        break;
+      case "title":
+        options.defaultTitle = value;
+        break;
+      default:
+        options[name] = value;
+        break;
+    }
+  }
+
+  return {
+    source,
+    target,
+    options,
+  };
+}
diff --git a/package.json b/package.json
index cd656ffc..d46ebc98 100644
--- a/package.json
+++ b/package.json
@@ -35,7 +35,7 @@
   },
   "scripts": {
     "build": "node lib/transform.js",
-    "pretest": "node lib/cli.js -p --skipBatchPath -t examples/PingTest_V1.no-batch.openapi3.json examples/PingTest_V1.xml",
+    "pretest": "rm examples/PingTest_V1.no-batch.openapi3.json && node lib/cli.js -p --skipBatchPath -t examples/PingTest_V1.no-batch.openapi3.json examples/PingTest_V1.xml",
     "test": "c8 mocha",
     "watch": "mocha --watch"
   },
diff --git a/test/cliParts.test.js b/test/cliParts.test.js
new file mode 100644
index 00000000..a1ff1d9e
--- /dev/null
+++ b/test/cliParts.test.js
@@ -0,0 +1,160 @@
+const assert = require("assert");
+
+const { parseArgs } = require("../lib/cliParts");
+
+describe("CLI parameters", function () {
+  it("no arguments", function () {
+    const args = parseArgs([]);
+    assert.deepStrictEqual(args.unknown, []);
+    assert.match(args.usage, /Usage:/);
+  });
+
+  it("help", function () {
+    const args = parseArgs(["-h"]);
+    assert.deepStrictEqual(args.unknown, []);
+    assert.match(args.usage, /Usage:/);
+
+    const args2 = parseArgs(["--help", "foo"]);
+    assert.deepStrictEqual(args2.unknown, []);
+    assert.match(args2.usage, /Usage:/);
+  });
+
+  it("unknown option", function () {
+    const args = parseArgs(["--do-not-know", "foo", "--whatever", "bar"]);
+    assert.deepStrictEqual(args.unknown, ["--do-not-know", "--whatever"]);
+    assert.match(args.usage, /Usage:/);
+  });
+
+  it("just the source", function () {
+    assert.deepStrictEqual(parseArgs(["foo"]), {
+      source: "foo",
+      target: "foo.openapi3.json",
+      options: {},
+    });
+
+    assert.deepStrictEqual(parseArgs([".foo"]), {
+      source: ".foo",
+      target: ".foo.openapi3.json",
+      options: {},
+    });
+
+    assert.deepStrictEqual(parseArgs(["foo.bar"]), {
+      source: "foo.bar",
+      target: "foo.openapi3.json",
+      options: {},
+    });
+  });
+
+  it("source and target", function () {
+    assert.deepStrictEqual(parseArgs(["foo", "-t", "bar"]), {
+      source: "foo",
+      target: "bar",
+      options: {},
+    });
+
+    assert.deepStrictEqual(parseArgs(["-t", "bar", "foo"]), {
+      source: "foo",
+      target: "bar",
+      options: {},
+    });
+  });
+
+  it("two sources", function () {
+    const args = parseArgs(["foo", "bar"]);
+    assert.deepStrictEqual(args.unknown, []);
+    assert.match(args.usage, /Usage:/);
+  });
+
+  it("pretty", function () {
+    assert.deepStrictEqual(parseArgs(["foo", "-p"]).options, {
+      pretty: true,
+    });
+    assert.deepStrictEqual(parseArgs(["--pretty", "foo"]).options, {
+      pretty: true,
+    });
+  });
+
+  it("all flags on", function () {
+    assert.deepStrictEqual(parseArgs(["-dp", "foo"]).options, {
+      diagram: true,
+      pretty: true,
+    });
+    assert.deepStrictEqual(parseArgs(["-d", "-p", "foo"]).options, {
+      diagram: true,
+      pretty: true,
+    });
+    assert.deepStrictEqual(
+      parseArgs(["--diagram", "--pretty", "foo"]).options,
+      {
+        diagram: true,
+        pretty: true,
+      },
+    );
+  });
+
+  it("service root", function () {
+    assert.deepStrictEqual(
+      parseArgs([
+        "--scheme",
+        "http",
+        "--host",
+        "localhost",
+        "--basePath",
+        "/root",
+        "foo",
+      ]).options,
+      {
+        scheme: "http",
+        host: "localhost",
+        basePath: "/root",
+      },
+    );
+  });
+
+  it("title & description & skip batch", function () {
+    assert.deepStrictEqual(
+      parseArgs([
+        "--title",
+        "Title",
+        "--description",
+        "Description",
+        "--skipBatchPath",
+        "foo",
+      ]).options,
+      {
+        defaultTitle: "Title",
+        defaultDescription: "Description",
+        skipBatchPath: true,
+      },
+    );
+  });
+
+  it("openapi-version", function () {
+    assert.deepStrictEqual(parseArgs(["-o", "4.0", "foo"]).options, {
+      openapiVersion: "4.0",
+    });
+    assert.deepStrictEqual(
+      parseArgs(["--openapi-version", "4.0", "foo"]).options,
+      {
+        openapiVersion: "4.0",
+      },
+    );
+  });
+
+  it("recursion levels", function () {
+    assert.deepStrictEqual(parseArgs(["--levels", "42", "foo"]).options, {
+      maxLevels: 42,
+    });
+    assert.deepStrictEqual(parseArgs(["--levels", "max", "foo"]).options, {});
+  });
+
+  it("root resources to keep", function () {
+    assert.deepStrictEqual(parseArgs(["--keep", "one", "foo"]).options, {
+      rootResourcesToKeep: ["one"],
+    });
+    assert.deepStrictEqual(
+      parseArgs(["--k", "first", "--keep", "second", "foo"]).options,
+      { rootResourcesToKeep: ["first", "second"] },
+    );
+  });
+});