test_runner: add code coverage support to spec reporter

Author: pulkit-30

lib/internal/test_runner/reporter/spec.js

@@ -6,11 +6,13 @@ const {
   ArrayPrototypeShift,
   ArrayPrototypeUnshift,
   hardenRegExp,
+  NumberPrototypeToFixed,
   RegExpPrototypeSymbolSplit,
   SafeMap,
   StringPrototypeRepeat,
 } = primordials;
 const assert = require('assert');
+const { relative } = require('path');
 const Transform = require('internal/streams/transform');
 const { inspectWithNoCustomRetry } = require('internal/errors');
 const { green, blue, red, white, gray } = require('internal/util/colors');
@@ -23,12 +25,14 @@ const colors = {
   'test:fail': red,
   'test:pass': green,
   'test:diagnostic': blue,
+  'test:coverage': blue,
 };
 const symbols = {
   '__proto__': null,
   'test:fail': '\u2716 ',
   'test:pass': '\u2714 ',
   'test:diagnostic': '\u2139 ',
+  'test:coverage': '\u2139 ',
   'arrow:right': '\u25B6 ',
 };
 class SpecReporter extends Transform {
@@ -59,6 +63,36 @@ class SpecReporter extends Transform {
       ), `\n${indent}  `);
     return `\n${indent}  ${message}\n`;
   }
+  #reportCoverage(color, nesting, summary, symbol) {
+    let report = `${color}${this.#indent(nesting)}${symbol}start of coverage report${white}\n`;
+    report += `${color}${this.#indent(nesting)}${symbol}file | line % | branch % | funcs % | uncovered lines${white}\n`;
+
+    for (let i = 0; i < summary.files.length; ++i) {
+      const {
+        path,
+        coveredLinePercent,
+        coveredBranchPercent,
+        coveredFunctionPercent,
+        uncoveredLineNumbers,
+      } = summary.files[i];
+      const relativePath = relative(summary.workingDirectory, path);
+      const lines = NumberPrototypeToFixed(coveredLinePercent, 2);
+      const branches = NumberPrototypeToFixed(coveredBranchPercent, 2);
+      const functions = NumberPrototypeToFixed(coveredFunctionPercent, 2);
+      const uncovered = ArrayPrototypeJoin(uncoveredLineNumbers, ', ');
+
+      report += `${color}${this.#indent(nesting)}${symbol}${relativePath} | ${lines} | ${branches} | ${functions} | ${uncovered}\n`;
+    }
+
+    const { totals } = summary;
+    report += `${color}${this.#indent(nesting)}${symbol}all files | ` +
+              `${NumberPrototypeToFixed(totals.coveredLinePercent, 2)} | ` +
+              `${NumberPrototypeToFixed(totals.coveredBranchPercent, 2)} | ` +
+              `${NumberPrototypeToFixed(totals.coveredFunctionPercent, 2)} |\n`;
+
+    report += `${color}${this.#indent(nesting)}${symbol}end of coverage report\n`;
+    return report;
+  }
   #handleEvent({ type, data }) {
     const color = colors[type] ?? white;
     const symbol = symbols[type] ?? ' ';
@@ -97,6 +131,8 @@ class SpecReporter extends Transform {
         break;
       case 'test:diagnostic':
         return `${color}${this.#indent(data.nesting)}${symbol}${data.message}${white}\n`;
+      case 'test:coverage':
+        return this.#reportCoverage(color, data.nesting, data.summary, symbol);
     }
   }
   _transform({ type, data }, encoding, callback) {