tests: split monolithic test.mjs into focused modules (#201)

- Add helpers.mjs with fixtures() path helper and mock setup functions
- Split into dependency-tree, formats, to-list, resolvers, node-modules,
  and config test files
- Add coverage for Sass nonExistent partials, _getDependencies parse errors,
  flat/scoped node_modules, requirejs nonExistent aliases, ES6 lazy/dynamic
  imports, nodeModulesConfig.entry, tsconfig/tsx/allowJs integration
- Flatten nested describes, inline single-use beforeEach() mocks, lift
  helpers to module scope, fix shadowed variables

Author: XhmikosR

package.json

@@ -16,7 +16,7 @@
   "scripts": {
     "lint": "xo",
     "fix": "xo --fix",
-    "mocha": "mocha",
+    "mocha": "mocha \"test/*.test.mjs\"",
     "test": "npm run lint && npm run mocha",
     "test:ci": "c8 npm run mocha"
   },
@@ -103,6 +103,14 @@
       "unicorn/prefer-module": "off",
       "unicorn/prefer-top-level-await": "off",
       "unicorn/prevent-abbreviations": "off"
-    }
+    },
+    "overrides": [
+      {
+        "files": "test/**/*.{c,m}js",
+        "envs": [
+          "mocha"
+        ]
+      }
+    ]
   }
 }

test/config.test.mjs

@@ -0,0 +1,74 @@
+import { strict as assert } from 'node:assert';
+import path from 'node:path';
+import Config from '../lib/config.js';
+import dependencyTree from '../index.js';
+import { fixtures } from './helpers.mjs';
+
+describe('noTypeDefinitions', () => {
+  const directory = fixtures('noTypeDefinitions');
+  const filename = path.join(directory, 'entrypoint.ts');
+
+  it('resolves to definition files when set to false', () => {
+    const list = dependencyTree.toList({
+      filename,
+      directory,
+      noTypeDefinitions: false
+    });
+
+    assert.ok(list.includes(path.join(directory, 'required.d.ts')));
+    assert.ok(!list.includes(path.join(directory, 'required.js')));
+  });
+
+  it('resolves to JavaScript files when set to true', () => {
+    const list = dependencyTree.toList({
+      filename,
+      directory,
+      noTypeDefinitions: true
+    });
+
+    assert.ok(list.includes(path.join(directory, 'required.js')));
+    assert.ok(!list.includes(path.join(directory, 'required.d.ts')));
+  });
+});
+
+describe('Config', () => {
+  it('pre-parses tsconfig for performance', () => {
+    const tsConfigPath = fixtures('ts', '.tsconfig');
+    const config = new Config({
+      filename: 'foo',
+      directory: 'bar',
+      tsConfig: tsConfigPath
+    });
+
+    assert.equal(typeof config.tsConfig, 'object');
+  });
+
+  it('includes tsConfigPath so filing-cabinet can resolve compilerOptions.paths', () => {
+    const tsConfigPath = fixtures('ts', '.tsconfig');
+    const config = new Config({
+      filename: 'foo',
+      directory: 'bar',
+      tsConfig: tsConfigPath
+    });
+
+    assert.equal(config.tsConfigPath, tsConfigPath);
+  });
+
+  it('retains detective config in the clone', () => {
+    const detectiveConfig = {
+      es6: {
+        mixedImports: true
+      }
+    };
+
+    const config = new Config({
+      detectiveConfig,
+      filename: 'foo',
+      directory: 'bar'
+    });
+
+    const clone = config.clone();
+
+    assert.deepEqual(clone.detectiveConfig, detectiveConfig);
+  });
+});