Add script for frontend test file coverage

package.json

@@ -7,6 +7,7 @@
     "eslint": "eslint --max-warnings 0 --report-unused-disable-directives --ext .js,.vue .",
     "eslint-fix": "eslint --max-warnings 0 --report-unused-disable-directives --ext .js,.vue --fix .",
     "eslint-report": "eslint --max-warnings 0 --ext .js,.vue --format html --output-file ./eslint-report.html --no-inline-config .",
+    "file-coverage": "scripts/frontend/file_test_coverage.js",
     "prejest": "yarn check-dependencies",
     "jest": "jest",
     "jest-debug": "node --inspect-brk node_modules/.bin/jest --runInBand",

scripts/frontend/file_test_coverage.js

+#!/usr/bin/env node
+
+/**
+ * Counts the number of frontend test files and compares them against the number of application files.
+ *
+ * Example output:
+ *
+ * Source files: 1551
+ * Test files: 716
+ * Coverage: 46.16%
+ */
+
+const fs = require('fs');
+const path = require('path');
+
+const sourceDirectories = ['app/assets/javascripts'];
+const testDirectories = ['spec/javascripts', 'spec/frontend'];
+
+if (fs.existsSync('ee')) {
+  sourceDirectories.forEach(dir => {
+    sourceDirectories.push(`ee/${dir}`);
+  });
+
+  testDirectories.forEach(dir => {
+    testDirectories.push(`ee/${dir}`);
+  });
+}
+
+let numSourceFiles = 0;
+let numTestFiles = 0;
+
+const isVerbose = process.argv.some(arg => arg === '-v');
+
+const countSourceFiles = path =>
+  forEachFileIn(path, fileName => {
+    if (fileName.endsWith('.vue') || fileName.endsWith('.js')) {
+      if (isVerbose) {
+        console.log(`source file: ${fileName}`);
+      }
+
+      numSourceFiles += 1;
+    }
+  });
+
+const countTestFiles = path =>
+  forEachFileIn(path, fileName => {
+    if (fileName.endsWith('_spec.js')) {
+      if (isVerbose) {
+        console.log(`test file: ${fileName}`);
+      }
+
+      numTestFiles += 1;
+    }
+  });
+
+function forEachFileIn(dirPath, callback) {
+  fs.readdir(dirPath, (err, files) => {
+    if (err) {
+      console.error(err);
+    }
+
+    if (!files) {
+      return;
+    }
+
+    files.forEach(fileName => {
+      const absolutePath = path.join(dirPath, fileName);
+      const stats = fs.statSync(absolutePath);
+      if (stats.isFile()) {
+        callback(absolutePath);
+      } else if (stats.isDirectory()) {
+        forEachFileIn(absolutePath, callback);
+      }
+    });
+  });
+}
+
+console.log(`Source directories: ${sourceDirectories.join(', ')}`);
+console.log(`Test directories: ${testDirectories.join(', ')}`);
+
+sourceDirectories.forEach(countSourceFiles);
+testDirectories.forEach(countTestFiles);
+
+process.on('exit', () => {
+  console.log(`Source files: ${numSourceFiles}`);
+  console.log(`Test files: ${numTestFiles}`);
+  console.log(`Coverage: ${((100 * numTestFiles) / numSourceFiles).toFixed(2)}%`);
+});