lint rules: move tests for hash_and_equals

Change-Id: Ib196e5ada71d5a822965e9bd1c01527d9cb10587
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/387523
Reviewed-by: Phil Quitslund <pquitslund@google.com>
Auto-Submit: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Phil Quitslund <pquitslund@google.com>

pkg/linter/test/rules/hash_and_equals_test.dart

@@ -67,6 +67,41 @@ enum A {
     ]);
   }
 
+  test_equalsEquals_andHashCode() async {
+    await assertNoDiagnostics(r'''
+class C {
+  @override
+  bool operator ==(Object other) => false;
+
+  @override
+  int get hashCode => 7;
+}
+''');
+  }
+
+  test_equalsEquals_andHashCodeField() async {
+    await assertNoDiagnostics(r'''
+class C {
+  @override
+  bool operator ==(Object other) => false;
+
+  @override
+  int hashCode = 7;
+}
+''');
+  }
+
+  test_equalsEquals_noHashCode() async {
+    await assertDiagnostics(r'''
+class C {
+  @override
+  bool operator ==(Object other) => false;
+}
+''', [
+      lint(38, 2),
+    ]);
+  }
+
   test_extensionType_missingHash() async {
     await assertDiagnostics(r'''
 extension type E(Object o) {
@@ -78,4 +113,32 @@ extension type E(Object o) {
           CompileTimeErrorCode.EXTENSION_TYPE_DECLARES_MEMBER_OF_OBJECT, 45, 2),
     ]);
   }
+
+  test_hashCode_noEqualsEquals() async {
+    await assertDiagnostics(r'''
+class C {
+  @override
+  int get hashCode => 7;
+}
+''', [
+      lint(32, 8),
+    ]);
+  }
+
+  test_hashCodeField_missingEqualsEquals() async {
+    await assertDiagnostics(r'''
+class C {
+  @override
+  final int hashCode = 7;
+}
+''', [
+      lint(34, 8),
+    ]);
+  }
+
+  test_neither() async {
+    await assertNoDiagnostics(r'''
+class C {}
+''');
+  }
 }