test: failing test for parsing a negative timestamp

Author: chingor13

google-cloud-core/src/test/java/com/google/cloud/TimestampTest.java

@@ -80,6 +80,30 @@ public void ofDate() {
     assertThat(timestamp.getNanos()).isEqualTo(expectedNanos);
   }
 
+  @Test
+  public void ofSqlTimestamp() {
+    String expectedTimestamp = "1970-01-01T00:00:12.345000000Z";
+    java.sql.Timestamp input = new java.sql.Timestamp(12345);
+    Timestamp timestamp = Timestamp.of(input);
+    assertThat(timestamp.toString()).isEqualTo(expectedTimestamp);
+  }
+
+  @Test
+  public void ofSqlTimestampPreEpoch() {
+    String expectedTimestamp = "1969-12-31T23:59:47.655000000Z";
+    java.sql.Timestamp input = new java.sql.Timestamp(-12345);
+    Timestamp timestamp = Timestamp.of(input);
+    assertThat(timestamp.toString()).isEqualTo(expectedTimestamp);
+  }
+
+  @Test
+  public void ofSqlTimestampOnEpoch() {
+    String expectedTimestamp = "1970-01-01T00:00:00Z";
+    java.sql.Timestamp input = new java.sql.Timestamp(0);
+    Timestamp timestamp = Timestamp.of(input);
+    assertThat(timestamp.toString()).isEqualTo(expectedTimestamp);
+  }
+
   @Test
   public void ofDatePreEpoch() {
     Timestamp timestamp = Timestamp.of(TEST_DATE_PRE_EPOCH);