test: remove tautological hashCode assertions and use idiomatic isEqualTo

- Remove self-comparing hashCode assertions (always true)
- Use assertThat(options).isEqualTo(options2) instead of
  assertThat(options.equals(options2)).isTrue() for better error messages

Author: anishesg

java-spanner/google-cloud-spanner/src/test/java/com/google/cloud/spanner/OptionsTest.java

@@ -152,11 +152,10 @@ public void allOptionsAbsent() {
     assertThat(options.equals(null)).isFalse();
     assertThat(options.equals(this)).isFalse();
     assertNull(options.isolationLevel());
-    // Verify hashCode contract: equal objects must have equal hashCodes, and hashCode is stable.
+    // Verify hashCode contract: equal objects must have equal hashCodes.
     Options options2 = Options.fromReadOptions();
-    assertThat(options.equals(options2)).isTrue();
+    assertThat(options).isEqualTo(options2);
     assertThat(options.hashCode()).isEqualTo(options2.hashCode());
-    assertThat(options.hashCode()).isEqualTo(options.hashCode());
   }
 
   @Test
@@ -179,13 +178,12 @@ public void listOptionsTest() {
     assertThat(options.pageSize()).isEqualTo(pageSize);
     assertThat(options.pageToken()).isEqualTo(pageToken);
     assertThat(options.filter()).isEqualTo(filter);
-    // Verify hashCode contract: equal objects must have equal hashCodes, and hashCode is stable.
+    // Verify hashCode contract: equal objects must have equal hashCodes.
     Options options2 =
         Options.fromListOptions(
             Options.pageSize(pageSize), Options.pageToken(pageToken), Options.filter(filter));
-    assertThat(options.equals(options2)).isTrue();
+    assertThat(options).isEqualTo(options2);
     assertThat(options.hashCode()).isEqualTo(options2.hashCode());
-    assertThat(options.hashCode()).isEqualTo(options.hashCode());
   }
 
   @Test
@@ -706,11 +704,10 @@ public void updateOptionsTest() {
     assertEquals("tag: " + tag + " ", options.toString());
     assertTrue(options.hasTag());
     assertThat(options.tag()).isEqualTo(tag);
-    // Verify hashCode contract: equal objects must have equal hashCodes, and hashCode is stable.
+    // Verify hashCode contract: equal objects must have equal hashCodes.
     Options options2 = Options.fromUpdateOptions(Options.tag(tag));
-    assertThat(options.equals(options2)).isTrue();
+    assertThat(options).isEqualTo(options2);
     assertThat(options.hashCode()).isEqualTo(options2.hashCode());
-    assertThat(options.hashCode()).isEqualTo(options.hashCode());
   }
 
   @Test
@@ -742,11 +739,10 @@ public void transactionOptionsTest() {
     assertEquals("tag: " + tag + " ", options.toString());
     assertTrue(options.hasTag());
     assertThat(options.tag()).isEqualTo(tag);
-    // Verify hashCode contract: equal objects must have equal hashCodes, and hashCode is stable.
+    // Verify hashCode contract: equal objects must have equal hashCodes.
     Options options2 = Options.fromTransactionOptions(Options.tag(tag));
-    assertThat(options.equals(options2)).isTrue();
+    assertThat(options).isEqualTo(options2);
     assertThat(options.hashCode()).isEqualTo(options2.hashCode());
-    assertThat(options.hashCode()).isEqualTo(options.hashCode());
   }
 
   @Test