Improve ObjectMapper configuration test coverage

Author: rammrain

src/test/java/ee/bitweb/core/object_mapper/Jackson2ObjectMapperCreatorIntegrationTests.java

@@ -0,0 +1,144 @@
+package ee.bitweb.core.object_mapper;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Tag;
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+
+import java.time.OffsetDateTime;
+import java.time.ZoneOffset;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+/**
+ * Integration tests for {@link ObjectMapperAutoConfiguration.Jackson2ObjectMapperCreator}.
+ *
+ * <p>Uses {@link ApplicationContextRunner} to create a lightweight context where no pre-existing
+ * {@code ObjectMapper} bean is defined, allowing the {@code @ConditionalOnMissingBean(ObjectMapper.class)}
+ * condition to be satisfied and the Creator inner class to activate.</p>
+ *
+ * <p>This scenario is never covered by the standard {@code @SpringBootTest} integration tests because
+ * {@code TestSpringApplication} always provides an {@code ObjectMapper} bean via Spring Boot auto-configuration.</p>
+ */
+@Tag("integration")
+class Jackson2ObjectMapperCreatorIntegrationTests {
+
+    private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
+            .withUserConfiguration(ObjectMapperAutoConfiguration.class)
+            .withPropertyValues("ee.bitweb.core.object-mapper.auto-configuration=true");
+
+    @Test
+    @DisplayName("Should load Jackson2ObjectMapperCreator inner class when no ObjectMapper exists")
+    void shouldLoadJackson2ObjectMapperCreatorBean() {
+        contextRunner.run(context -> {
+            assertThat(context).hasSingleBean(ObjectMapperAutoConfiguration.Jackson2ObjectMapperCreator.class);
+        });
+    }
+
+    @Test
+    @DisplayName("Should create ObjectMapper bean via Jackson2ObjectMapperCreator")
+    void shouldCreateObjectMapperBean() {
+        contextRunner.run(context -> {
+            assertThat(context).hasSingleBean(ObjectMapper.class);
+            assertThat(context).hasBean("objectMapper");
+        });
+    }
+
+    @Test
+    @DisplayName("Created ObjectMapper should trim strings during deserialization")
+    void shouldTrimStringsDuringDeserialization() {
+        contextRunner.run(context -> {
+            ObjectMapper objectMapper = context.getBean(ObjectMapper.class);
+            String json = "{\"value\": \"  trimmed  \"}";
+
+            TestDto result = objectMapper.readValue(json, TestDto.class);
+
+            assertThat(result.value).isEqualTo("trimmed");
+        });
+    }
+
+    @Test
+    @DisplayName("Created ObjectMapper should handle Java time types with JavaTimeModule")
+    void shouldHandleJavaTimeTypes() {
+        contextRunner.run(context -> {
+            ObjectMapper objectMapper = context.getBean(ObjectMapper.class);
+            String json = "{\"timestamp\": \"2024-01-15T10:30:00Z\"}";
+
+            TestDtoWithTime result = objectMapper.readValue(json, TestDtoWithTime.class);
+
+            assertThat(result.timestamp).isNotNull();
+            assertThat(result.timestamp.getYear()).isEqualTo(2024);
+            assertThat(result.timestamp.getMonthValue()).isEqualTo(1);
+            assertThat(result.timestamp.getDayOfMonth()).isEqualTo(15);
+        });
+    }
+
+    @Test
+    @DisplayName("Created ObjectMapper should have ADJUST_DATES_TO_CONTEXT_TIME_ZONE disabled")
+    void shouldHaveAdjustDatesToContextTimeZoneDisabled() {
+        contextRunner.run(context -> {
+            ObjectMapper objectMapper = context.getBean(ObjectMapper.class);
+
+            assertThat(objectMapper.isEnabled(DeserializationFeature.ADJUST_DATES_TO_CONTEXT_TIME_ZONE)).isFalse();
+        });
+    }
+
+    @Test
+    @DisplayName("Created ObjectMapper should have ACCEPT_FLOAT_AS_INT disabled")
+    void shouldHaveAcceptFloatAsIntDisabled() {
+        contextRunner.run(context -> {
+            ObjectMapper objectMapper = context.getBean(ObjectMapper.class);
+
+            assertThat(objectMapper.isEnabled(DeserializationFeature.ACCEPT_FLOAT_AS_INT)).isFalse();
+        });
+    }
+
+    @Test
+    @DisplayName("Created ObjectMapper should reject float value for integer field")
+    void shouldRejectFloatForIntegerField() {
+        contextRunner.run(context -> {
+            ObjectMapper objectMapper = context.getBean(ObjectMapper.class);
+            String json = "{\"count\": 1.5}";
+
+            assertThatThrownBy(() -> objectMapper.readValue(json, TestDtoWithInt.class))
+                    .isInstanceOf(JsonProcessingException.class);
+        });
+    }
+
+    @Test
+    @DisplayName("Created ObjectMapper should preserve timezone offset in deserialized date")
+    void shouldPreserveTimezoneInDate() {
+        contextRunner.run(context -> {
+            ObjectMapper objectMapper = context.getBean(ObjectMapper.class);
+            String json = "{\"timestamp\": \"2024-01-15T10:30:00+05:00\"}";
+
+            TestDtoWithTime result = objectMapper.readValue(json, TestDtoWithTime.class);
+
+            assertThat(result.timestamp.getOffset()).isEqualTo(ZoneOffset.ofHours(5));
+        });
+    }
+
+    @Test
+    @DisplayName("Jackson2ObjectMapperCustomizer should NOT be loaded when no pre-existing ObjectMapper exists")
+    void shouldNotLoadJackson2ObjectMapperCustomizerBean() {
+        contextRunner.run(context -> {
+            assertThat(context).doesNotHaveBean("objectMapperAutoConfiguration.Jackson2ObjectMapperCustomizer");
+        });
+    }
+
+    static class TestDto {
+        public String value;
+    }
+
+    static class TestDtoWithTime {
+        public OffsetDateTime timestamp;
+    }
+
+    static class TestDtoWithInt {
+        public Integer count;
+    }
+}