test_runner: print coverage and diagnostic info with dot reporter

lib/internal/test_runner/reporter/dot.js

@@ -4,12 +4,19 @@ const {
   MathMax,
 } = primordials;
 const colors = require('internal/util/colors');
-const { formatTestReport } = require('internal/test_runner/reporter/utils');
+const { getCoverageReport } = require('internal/test_runner/utils');
+const {
+  formatTestReport,
+  reporterColorMap,
+  reporterUnicodeSymbolMap,
+} = require('internal/test_runner/reporter/utils');
 
 module.exports = async function* dot(source) {
   let count = 0;
   let columns = getLineLength();
   const failedTests = [];
+  const diagnostics = [];
+  let coverage;
   for await (const { type, data } of source) {
     if (type === 'test:pass') {
       yield `${colors.green}.${colors.reset}`;
@@ -25,8 +32,24 @@ module.exports = async function* dot(source) {
       columns = getLineLength();
       count = 0;
     }
+    if (type === 'test:diagnostic' && data.level === 'error') {
+      ArrayPrototypePush(diagnostics, data);
+    }
+    if (type === 'test:coverage') {
+      coverage = data;
+    }
   }
   yield '\n';
+  if (diagnostics.length > 0) {
+    for (const diagnostic of diagnostics) {
+      const color = reporterColorMap[diagnostic.level] || reporterColorMap['test:diagnostic'];
+      yield `${color}${reporterUnicodeSymbolMap['test:diagnostic']}${diagnostic.message}${colors.white}\n`;
+    }
+    if (coverage) {
+      yield getCoverageReport('', coverage.summary,
+                              reporterUnicodeSymbolMap['test:coverage'], colors.blue, true);
+    }
+  }
   if (failedTests.length > 0) {
     yield `\n${colors.red}Failed tests:${colors.white}\n\n`;
     for (const test of failedTests) {

test/parallel/test-runner-coverage-thresholds.js

@@ -170,4 +170,25 @@ for (const coverage of coverages) {
     assert.strictEqual(result.status, 1);
     assert(!findCoverageFileForPid(result.pid));
   });
+
+  test(`test failing ${coverage.flag} with dot reporter`, () => {
+    const result = spawnSync(process.execPath, [
+      '--test',
+      '--experimental-test-coverage',
+      '--test-coverage-exclude=!test/**',
+      `${coverage.flag}=99`,
+      '--test-reporter', 'dot',
+      fixture,
+    ]);
+
+    const stdout = result.stdout.toString();
+    assert.match(
+      stdout,
+      RegExp(`Error: ${coverage.actual.toFixed(2)}% ${coverage.name} coverage does not meet threshold of 99%`)
+    );
+    assert.match(stdout, /start of coverage report/);
+    assert.match(stdout, /end of coverage report/);
+    assert.strictEqual(result.status, 1);
+    assert(!findCoverageFileForPid(result.pid));
+  });
 }