Test @DefaultTimeZone for misconfiguration (#164 / #272)

Progresses: #164
PR: #272

src/main/java/org/junitpioneer/jupiter/DefaultTimeZoneExtension.java

@@ -16,6 +16,7 @@
 import org.junit.jupiter.api.extension.AfterEachCallback;
 import org.junit.jupiter.api.extension.BeforeAllCallback;
 import org.junit.jupiter.api.extension.BeforeEachCallback;
+import org.junit.jupiter.api.extension.ExtensionConfigurationException;
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.ExtensionContext.Namespace;
 import org.junit.jupiter.api.extension.ExtensionContext.Store;
@@ -42,8 +43,21 @@ public void beforeEach(ExtensionContext context) {
 
 	private void setDefaultTimeZone(Store store, DefaultTimeZone annotation) {
 		storeDefaultTimeZone(store);
-		TimeZone configuredTimeZone = TimeZone.getTimeZone(annotation.value());
-		TimeZone.setDefault(configuredTimeZone);
+		String timeZoneId = annotation.value();
+		TimeZone.setDefault(getTimeZone(timeZoneId));
+	}
+
+	private TimeZone getTimeZone(String timeZoneId) {
+		TimeZone configuredTimeZone = TimeZone.getTimeZone(timeZoneId);
+		// TimeZone::getTimeZone returns with GMT as fallback if the given ID cannot be understood
+		if (configuredTimeZone.equals(TimeZone.getTimeZone("GMT")) && !timeZoneId.equals("GMT")) {
+			throw new ExtensionConfigurationException(String
+					.format("@DefaultTimeZone not configured correctly. "
+							+ "Could not find the specified time zone + '%s'. "
+							+ "Please use correct identifiers, e.g. \"GMT\" for Greenwich Mean Time.",
+						timeZoneId));
+		}
+		return configuredTimeZone;
 	}
 
 	private void storeDefaultTimeZone(Store store) {

src/test/java/org/junitpioneer/jupiter/DefaultTimeZoneTests.java

@@ -11,7 +11,9 @@
 package org.junitpioneer.jupiter;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.fail;
 import static org.junitpioneer.testkit.PioneerTestKit.executeTestClass;
+import static org.junitpioneer.testkit.PioneerTestKit.executeTestMethod;
 
 import java.util.TimeZone;
 
@@ -22,6 +24,7 @@
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtensionConfigurationException;
 import org.junitpioneer.testkit.ExecutionResults;
 
 @DisplayName("DefaultTimeZone extension")
@@ -60,6 +63,25 @@ void doesNothingWhenAnnotationNotPresent() {
 			assertThat(TimeZone.getDefault()).isEqualTo(TEST_DEFAULT_TIMEZONE);
 		}
 
+		@Test
+		@DisplayName("throws exception on bad configuration")
+		void throwsWhenConfigurationIsBad() {
+			ExecutionResults results = executeTestMethod(BadMethodLevelConfigurationTestCase.class, "badConfiguration");
+
+			assertThat(results.numberOfFailedTests()).isEqualTo(1);
+			assertThat(results.firstFailuresThrowable()).isExactlyInstanceOf(ExtensionConfigurationException.class);
+			assertThat(results.firstFailuresThrowableMessage())
+					.doesNotContain("should never execute")
+					.contains("@DefaultTimeZone not configured correctly.");
+		}
+
+		@DefaultTimeZone("GMT")
+		@Test
+		@DisplayName("does not throw when explicitly set to GMT")
+		void doesNotThrowForExplicitGmt() {
+			assertThat(TimeZone.getDefault()).isEqualTo(TimeZone.getTimeZone("GMT"));
+		}
+
 		@DefaultTimeZone("CET")
 		@Test
 		@DisplayName("sets the default time zone using an abbreviation")
@@ -86,13 +108,31 @@ void setUp() {
 		}
 
 		@Test
-		@DisplayName("should execute tests with configured TimeZone")
+		@DisplayName("executes tests with configured TimeZone")
 		void shouldExecuteTestsWithConfiguredTimeZone() {
 			ExecutionResults results = executeTestClass(ClassLevelTestCase.class);
 
 			assertThat(results.numberOfSucceededTests()).isEqualTo(2);
 		}
 
+		@Test
+		@DisplayName("throws when configuration is bad")
+		void shouldThrowWithBadConfiguration() {
+			ExecutionResults results = executeTestClass(BadClassLevelConfigurationTestCase.class);
+
+			assertThat(results.numberOfStartedTests()).isEqualTo(0);
+			assertThat(results.firstFailuresThrowable()).isExactlyInstanceOf(ExtensionConfigurationException.class);
+			assertThat(results.firstFailuresThrowableMessage()).contains("@DefaultTimeZone not configured correctly.");
+		}
+
+		@Test
+		@DisplayName("does not throw when explicitly set to GMT")
+		void shouldNotThrowForExplicitGmt() {
+			ExecutionResults results = executeTestClass(ExplicitGmtClassLevelTestCase.class);
+
+			assertThat(results.numberOfSucceededTests()).isEqualTo(1);
+		}
+
 		@AfterEach
 		void tearDown() {
 			assertThat(TimeZone.getDefault()).isEqualTo(TEST_DEFAULT_TIMEZONE);
@@ -155,4 +195,34 @@ public void shouldSetTimeZoneFromMethodOfNestedClass() {
 
 	}
 
+	static class BadMethodLevelConfigurationTestCase {
+
+		@DefaultTimeZone("Gibberish")
+		@Test
+		void badConfiguration() {
+			fail("This test should never execute");
+		}
+
+	}
+
+	@DefaultTimeZone("Gibberish")
+	static class BadClassLevelConfigurationTestCase {
+
+		@Test
+		void badConfiguration() {
+			fail("This test should never execute");
+		}
+
+	}
+
+	@DefaultTimeZone("GMT")
+	static class ExplicitGmtClassLevelTestCase {
+
+		@Test
+		void explicitGmt() {
+			assertThat(TimeZone.getDefault()).isEqualTo(TimeZone.getTimeZone("GMT"));
+		}
+
+	}
+
 }