test_runner: omit inaccessible files from coverage

lib/internal/test_runner/coverage.js

@@ -99,7 +99,16 @@ class TestCoverage {
       // original line endings because those characters are necessary for
       // determining offsets in the file.
       const filePath = fileURLToPath(url);
-      const source = readFileSync(filePath, 'utf8');
+      let source;
+
+      try {
+        source = readFileSync(filePath, 'utf8');
+      } catch {
+        // The file can no longer be read. It may have been deleted among
+        // other possibilities. Leave it out of the coverage report.
+        continue;
+      }
+
       const linesWithBreaks =
         RegExpPrototypeSymbolSplit(kLineSplitRegex, source);
       let ignoreCount = 0;

test/fixtures/v8-coverage/combined_coverage/third.test.js

@@ -1,8 +1,25 @@
 'use strict';
+const assert = require('node:assert');
+const { unlinkSync, writeFileSync } = require('node:fs')
+const { join } = require('node:path');
 const { test } = require('node:test');
 const common = require('./common');
 
 test('third 1', () => {
   common.fnC(1, 4);
   common.fnD(99);
 });
+
+assert(process.env.NODE_TEST_TMPDIR);
+const tmpFilePath = join(process.env.NODE_TEST_TMPDIR, 'temp-module.js');
+writeFileSync(tmpFilePath, `
+  module.exports = {
+    fn() {
+      return 42;
+    }
+  };
+`);
+const tempModule = require(tmpFilePath);
+assert.strictEqual(tempModule.fn(), 42);
+// Deleted files should not be part of the coverage report.
+unlinkSync(tmpFilePath);

test/parallel/test-runner-coverage.js

@@ -156,7 +156,7 @@ test('coverage is combined for multiple processes', skipIfNoInspector, () => {
     '| 100.00 | 100.00 | ',
     '# test/fixtures/v8-coverage/combined_coverage/third.test.js | 100.00 | ' +
     '100.00 | 100.00 | ',
-    '# all files | 90.72 | 72.73 | 88.89 |',
+    '# all files | 92.11 | 72.73 | 88.89 |',
     '# end of coverage report',
   ].join('\n');
 
@@ -168,7 +168,9 @@ test('coverage is combined for multiple processes', skipIfNoInspector, () => {
   const args = [
     '--test', '--experimental-test-coverage', '--test-reporter', 'tap', fixture,
   ];
-  const result = spawnSync(process.execPath, args);
+  const result = spawnSync(process.execPath, args, {
+    env: { ...process.env, NODE_TEST_TMPDIR: tmpdir.path }
+  });
 
   assert.strictEqual(result.stderr.toString(), '');
   assert(result.stdout.toString().includes(report));