Initial migration of SystemPropertyExtension

Needs rebase after merge of LocaleExtension

Author: Bukama

documentation/src/docs/asciidoc/user-guide/writing-tests.adoc

@@ -0,0 +1,153 @@
+/*
+ * Copyright 2015-2025 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+package example;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.ClassOrderer;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Order;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestClassOrder;
+import org.junit.jupiter.api.TestInstance;
+import org.junit.jupiter.api.system.ClearSystemProperty;
+import org.junit.jupiter.api.system.ReadsSystemProperty;
+import org.junit.jupiter.api.system.RestoreSystemProperties;
+import org.junit.jupiter.api.system.SetSystemProperty;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+public class SystemPropertyExtensionDemo {
+
+	// tag::systemproperty_clear_simple[]
+	@Test
+	@ClearSystemProperty(key = "some property")
+	void testClearingProperty() {
+		assertThat(System.getProperty("some property")).isNull();
+	}
+	// end::systemproperty_clear_simple[]
+
+	// tag::systemproperty_set_simple[]
+	@Test
+	@SetSystemProperty(key = "some property", value = "new value")
+	void testSettingProperty() {
+		assertThat(System.getProperty("some property")).isEqualTo("new value");
+	}
+	// end::systemproperty_set_simple[]
+
+	// tag::systemproperty_using_set_and_clear[]
+	@Test
+	@ClearSystemProperty(key = "1st property")
+	@ClearSystemProperty(key = "2nd property")
+	@SetSystemProperty(key = "3rd property", value = "new value")
+	void testClearingAndSettingProperty() {
+		assertThat(System.getProperty("1st property")).isNull();
+		assertThat(System.getProperty("2nd property")).isNull();
+		assertThat(System.getProperty("3rd property")).isEqualTo("new value");
+	}
+	// end::systemproperty_using_set_and_clear[]
+
+	@Nested
+	// tag::systemproperty_using_at_class_level[]
+	@ClearSystemProperty(key = "some property")
+	class MySystemPropertyTest {
+
+		@Test
+		@SetSystemProperty(key = "some property", value = "new value")
+		void clearedAtClasslevel() {
+			assertThat(System.getProperty("some property")).isEqualTo("new value");
+		}
+
+	}
+	// end::systemproperty_using_at_class_level[]
+
+	// tag::systemproperty_restore_test[]
+	@ParameterizedTest
+	@ValueSource(strings = { "foo", "bar" })
+	@RestoreSystemProperties
+	void parameterizedTest(String value) {
+		System.setProperty("some parameterized property", value);
+		System.setProperty("some other dynamic property", "my code calculates somehow");
+	}
+	// end::systemproperty_restore_test[]
+
+	@Nested
+	@TestClassOrder(ClassOrderer.OrderAnnotation.class)
+	class SystemPropertyRestoreExample {
+
+		@Nested
+		@Order(1)
+		@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+		// tag::systemproperty_class_restore_setup[]
+		@RestoreSystemProperties
+		class MySystemPropertyRestoreTest {
+
+			@BeforeAll
+			void beforeAll() {
+				System.setProperty("A", "A value");
+			}
+
+			@BeforeEach
+			void beforeEach() {
+				System.setProperty("B", "B value");
+			}
+
+			@Test
+			void isolatedTest1() {
+				System.setProperty("C", "C value");
+			}
+
+			@Test
+			void isolatedTest2() {
+				assertThat(System.getProperty("A")).isEqualTo("A value");
+				assertThat(System.getProperty("B")).isEqualTo("B value");
+
+				// Class-level @RestoreSystemProperties restores "C" to original state
+				assertThat(System.getProperty("C")).isNull();
+			}
+
+		}
+		// end::systemproperty_class_restore_setup[]
+
+		@Nested
+		@Order(2)
+		// tag::systemproperty_class_restore_isolated_class[]
+		@ReadsSystemProperty
+		class SomeOtherTestClass {
+
+			@Test
+			void isolatedTest() {
+				assertThat(System.getProperty("A")).isNull();
+				assertThat(System.getProperty("B")).isNull();
+				assertThat(System.getProperty("C")).isNull();
+			}
+
+		}
+
+		// end::systemproperty_class_restore_isolated_class[]
+	}
+
+	// tag::systemproperty_method_combine_all_test[]
+	@ParameterizedTest
+	@ValueSource(ints = { 100, 500, 1000 })
+	@RestoreSystemProperties
+	@SetSystemProperty(key = "DISABLE_CACHE", value = "TRUE")
+	@ClearSystemProperty(key = "COPYWRITE_OVERLAY_TEXT")
+	void imageGenerationTest(int imageSize) {
+		System.setProperty("IMAGE_SIZE", String.valueOf(imageSize)); // Requires restore
+
+		// Test your image generation utility with the current system properties
+	}
+	// end::systemproperty_method_combine_all_test[]
+
+}

documentation/src/test/java/example/SystemPropertyExtensionDemo.java

@@ -33,4 +33,5 @@
 	exports org.junit.jupiter.api.timeout to org.junit.jupiter.engine;
 
 	opens org.junit.jupiter.api.condition to org.junit.platform.commons;
+	exports org.junit.jupiter.api.system to org.junit.jupiter.engine;
 }