test: add coverage options file locator tests

pkgs/coverage/test/config_file_locator_test.dart

@@ -0,0 +1,45 @@
+import 'dart:io';
+import 'package:coverage/src/coverage_options.dart';
+import 'package:path/path.dart' as path;
+import 'package:test/test.dart';
+
+void main() {
+  final baseTestPath = 'test/test_file_locator';
+  late Directory testDirectory;
+
+  test('options file exists', () {
+    testDirectory = Directory('$baseTestPath/pkg1/lib/src');
+    var filePath =
+        CoverageOptionsProvider.findOptionsFilePath(directory: testDirectory);
+    expect(path.normalize('$baseTestPath/pkg1/coverage_options.yaml'),
+        path.normalize(filePath!));
+
+    testDirectory = Directory('$baseTestPath/pkg1/lib');
+    filePath =
+        CoverageOptionsProvider.findOptionsFilePath(directory: testDirectory);
+    expect(path.normalize('$baseTestPath/pkg1/coverage_options.yaml'),
+        path.normalize(filePath!));
+  });
+
+  test('options file missing', () {
+    testDirectory = Directory('$baseTestPath/pkg2/lib/src');
+    var filePath =
+        CoverageOptionsProvider.findOptionsFilePath(directory: testDirectory);
+    expect(filePath, isNull);
+
+    testDirectory = Directory('$baseTestPath/pkg2/lib');
+    filePath =
+        CoverageOptionsProvider.findOptionsFilePath(directory: testDirectory);
+    expect(filePath, isNull);
+  });
+
+  test('no pubspec found', () {
+    var filePath = CoverageOptionsProvider.findOptionsFilePath(
+        directory: Directory.systemTemp);
+    expect(filePath, isNull);
+
+    filePath = CoverageOptionsProvider.findOptionsFilePath(
+        directory: Directory.systemTemp);
+    expect(filePath, isNull);
+  });
+}