test_runner: support coverage of unnamed functions

This commit updates the code coverage logic to skip the first
function in a file (which does not correspond to an actual
function) instead of skipping all functions without a name.

PR-URL: nodejs#47652
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

lib/internal/test_runner/coverage.js

@@ -155,7 +155,7 @@ class TestCoverage {
       });
 
       for (let j = 0; j < functions.length; ++j) {
-        const { functionName, isBlockCoverage, ranges } = functions[j];
+        const { isBlockCoverage, ranges } = functions[j];
 
         for (let k = 0; k < ranges.length; ++k) {
           const range = ranges[k];
@@ -172,7 +172,7 @@ class TestCoverage {
           }
         }
 
-        if (functionName.length > 0 && ranges.length > 0) {
+        if (j > 0 && ranges.length > 0) {
           const range = ranges[0];
 
           if (range.count !== 0 || range.ignoredLines === range.lines.length) {

test/fixtures/test-runner/coverage.js

@@ -29,7 +29,7 @@ if (false) {
   require('./invalid-tap.js');
 }
 
-test('a test', function testHandler() {
+test('a test', () => {
   const uncalled = () => {};
 
   function fnWithControlFlow(val) {