Refactor generate-artifacts to improve testability.

Summary:
This Diff splits the `generate-artifacts.js` script into:
* `generate-artifacts-executor.js`: which contains the logic to generate the code for iOS.
* `generate-artifacts.js`: which contains the argument parsing logic and invokes the executor.

Finally, it introduces some tests.

## Changelog
[iOS][Changed] - Refactor part of the codegen scripts and add tests.

Reviewed By: cortinico, dmitryrykun

Differential Revision: D35846674

fbshipit-source-id: 14873c3fe762606e9004a29e4a6b986bf6a8f055

scripts/codegen/__tests__/generate-artifacts-executor-test.js

@@ -0,0 +1,99 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails oncall+react_native
+ * @format
+ */
+
+'use strict';
+
+const underTest = require('../generate-artifacts-executor');
+const path = require('path');
+
+describe('generateCode', () => {
+  it('executeNodes with the right arguents', () => {
+    // Define variables and expected values
+    const iosOutputDir = 'app/ios/build/generated/ios';
+    const library = {config: {name: 'library', type: 'all'}};
+    const tmpDir = 'tmp';
+    const node = 'usr/bin/node';
+    const pathToSchema = 'app/build/schema.json';
+    const rnRoot = path.join(__dirname, '../..');
+    const libraryType = 'all';
+
+    const tmpComponentOutDirs = path.join(tmpDir, 'out', 'components');
+    const tmpNativeModulesOutDir = path.join(tmpDir, 'out', 'nativeModules');
+    const iOSComponentOutDirs = path.join(
+      iosOutputDir,
+      'react/renderer/components',
+      library.config.name,
+    );
+    const iOSNativeModulesOutDir = path.join(
+      iosOutputDir,
+      './',
+      library.config.name,
+    );
+
+    // mock used functions
+    let mkdirSyncInvocationCount = 0;
+    jest.mock('fs', () => ({
+      readdirSync: dirpath => {
+        return ['test/dir']; //we only require to return something, so that the folder is not empty.
+      },
+      mkdirSync: (location, config) => {
+        if (mkdirSyncInvocationCount === 0) {
+          expect(location).toEqual(tmpComponentOutDirs);
+        }
+        if (mkdirSyncInvocationCount === 1) {
+          expect(location).toEqual(tmpNativeModulesOutDir);
+        }
+        if (mkdirSyncInvocationCount === 2) {
+          expect(location).toEqual(iOSComponentOutDirs);
+        }
+        if (mkdirSyncInvocationCount === 3) {
+          expect(location).toEqual(iOSNativeModulesOutDir);
+        }
+        mkdirSyncInvocationCount += 1;
+      },
+    }));
+
+    let execSyncInvocationCount = 0;
+    jest.mock('child_process', () => ({
+      execSync: command => {
+        if (execSyncInvocationCount === 0) {
+          const expectedCommand = `${node} ${path.join(
+            rnRoot,
+            'generate-specs-cli.js',
+          )} \
+        --platform ios \
+        --schemaPath ${pathToSchema} \
+        --outputDir ${tmpNativeModulesOutDir} \
+        --componentsOutputDir ${tmpComponentOutDirs} \
+        --modulesOutputDirs ${tmpNativeModulesOutDir} \
+        --libraryName ${library.config.name} \
+        --libraryType ${libraryType}`;
+          expect(command).toEqual(expectedCommand);
+        }
+
+        if (execSyncInvocationCount === 1) {
+          expect(command).toEqual(
+            `cp -R ${tmpComponentOutDirs}/* ${iOSComponentOutDirs}`,
+          );
+        }
+        if (execSyncInvocationCount === 2) {
+          expect(command).toEqual(
+            `cp -R ${tmpNativeModulesOutDir}/* ${iOSNativeModulesOutDir}`,
+          );
+        }
+
+        execSyncInvocationCount += 1;
+      },
+    }));
+
+    underTest._generateCode(iosOutputDir, library, tmpDir, node, pathToSchema);
+    expect(mkdirSyncInvocationCount).toBe(4);
+  });
+});