Improve resolver test coverage

Author: liamappelbe

test/resolver_test.dart

@@ -42,6 +42,18 @@ void main() {
           d.file('foo.dart', 'final foo = "bar";'),
         ]),
       ]).create();
+
+      await d.dir('sdk', [
+        d.dir('io', [
+          d.file('io.dart', 'final io = "hello";'),
+        ]),
+        d.dir('io_patch', [
+          d.file('io.dart', 'final patch = true;'),
+        ]),
+        d.dir('io_dev', [
+          d.file('io.dart', 'final dev = true;'),
+        ]),
+      ]).create();
     });
 
     test('can be created from a package_config.json', () async {
@@ -68,6 +80,41 @@ void main() {
                   d.sandbox, 'foo', '.dart_tool', 'bad_package_config.json')),
           throwsA(isA<FormatException>()));
     });
+
+    test('resolves dart: URIs', () async {
+      final resolver = await Resolver.create(
+          packagePath: p.join(d.sandbox, 'foo'),
+          sdkRoot: p.join(d.sandbox, 'sdk'));
+      expect(resolver.resolve('dart:io'),
+          p.join(d.sandbox, 'sdk', 'io', 'io.dart'));
+      expect(resolver.resolve('dart:io-patch/io.dart'), null);
+      expect(resolver.resolve('dart:io-dev/io.dart'),
+          p.join(d.sandbox, 'sdk', 'io_dev', 'io.dart'));
+    });
+
+    test('cannot resolve SDK URIs if sdkRoot is null', () async {
+      final resolver =
+          await Resolver.create(packagePath: p.join(d.sandbox, 'foo'));
+      expect(resolver.resolve('dart:convert'), null);
+    });
+
+    test('cannot resolve package URIs if packagePath is null', () async {
+      // ignore: deprecated_member_use_from_same_package
+      final resolver = Resolver();
+      expect(resolver.resolve('package:foo/foo.dart'), null);
+    });
+
+    test('cannot resolve package URIs if packagePath is not found', () async {
+      final resolver =
+          await Resolver.create(packagePath: p.join(d.sandbox, 'foo'));
+      expect(resolver.resolve('package:baz/baz.dart'), null);
+    });
+
+    test('cannot resolve unexpected URI schemes', () async {
+      final resolver =
+          await Resolver.create(packagePath: p.join(d.sandbox, 'foo'));
+      expect(resolver.resolve('thing:foo/foo.dart'), null);
+    });
   });
 
   group('Bazel resolver', () {