test: add snapshot test for dot reporter coverage threshold

Author: mag123c

test/fixtures/test-runner/output/dot_reporter_coverage_threshold.js

@@ -0,0 +1,17 @@
+'use strict';
+require('../../../common');
+const fixtures = require('../../../common/fixtures');
+const spawn = require('node:child_process').spawn;
+
+spawn(
+  process.execPath,
+  [
+    '--no-warnings',
+    '--experimental-test-coverage',
+    '--test-coverage-exclude=!test/**',
+    '--test-coverage-lines=99',
+    '--test-reporter', 'dot',
+    fixtures.path('test-runner/coverage.js'),
+  ],
+  { stdio: 'inherit' },
+);

test/fixtures/test-runner/output/dot_reporter_coverage_threshold.snapshot

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+invalid tap output
+.
+ℹ Error: 78.35% line coverage does not meet threshold of 99%.
+ℹ start of coverage report
+ℹ --------------------------------------------------------------------------------------------
+ℹ file              | line % | branch % | funcs % | uncovered lines
+ℹ --------------------------------------------------------------------------------------------
+ℹ test              |        |          |         | 
+ℹ  fixtures         |        |          |         | 
+ℹ   test-runner     |        |          |         | 
+ℹ    coverage.js    |  78.65 |    38.46 |   60.00 | 12-13 16-22 27 39 43-44 61-62 66-67 71-72
+ℹ    invalid-tap.js | 100.00 |   100.00 |  100.00 | 
+ℹ   v8-coverage     |        |          |         | 
+ℹ    throw.js       |  71.43 |    50.00 |  100.00 | 5-6
+ℹ --------------------------------------------------------------------------------------------
+ℹ all files         |  78.35 |    43.75 |   60.00 | 
+ℹ --------------------------------------------------------------------------------------------
+ℹ end of coverage report

test/test-runner/test-output-dot-reporter-coverage-threshold.mjs

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+// Test that the output of test-runner/output/dot_reporter_coverage_threshold.js matches
+// test-runner/output/dot_reporter_coverage_threshold.snapshot
+import * as common from '../common/index.mjs';
+import * as fixtures from '../common/fixtures.mjs';
+import { spawnAndAssert, specTransform, ensureCwdIsProjectRoot } from '../common/assertSnapshot.js';
+
+if (!process.features.inspector) {
+  common.skip('inspector support required');
+}
+
+ensureCwdIsProjectRoot();
+await spawnAndAssert(
+  fixtures.path('test-runner/output/dot_reporter_coverage_threshold.js'),
+  specTransform,
+);