ClockRule: Migrate to ClockExtension

Currently, we use ClockRule to implement a clock for unit testing.

Rules are part of JUnit 4, and have been replaced by extensions in JUnit 5. As we migrate to JUnit 5, we should update ClockRule to follow the new naming convenion and use JUnit 5 extension style.

Let's rewrite ClockRule to implement an injectable clock using JUnit5 callbacks.

src/test/java/systemtests/AddressBookSystemTest.java

@@ -16,10 +16,10 @@
 import java.util.Date;
 import java.util.List;
 
-import org.junit.ClassRule;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.extension.RegisterExtension;
 import org.junit.jupiter.api.io.TempDir;
 
 import guitests.guihandles.BrowserPanelHandle;
@@ -46,15 +46,16 @@
  * for test verification.
  */
 public abstract class AddressBookSystemTest {
-    @ClassRule
-    public static ClockRule clockRule = new ClockRule();
 
     @TempDir
     public static Path tempDir;
 
     public static final String SAVE_FILENAME_FOR_TESTING = "sampleData.json";
     public static final String CONFIG_FILENAME_FOR_TESTING = "pref_testing.json";
 
+    @RegisterExtension
+    public static ClockExtension clockExtension = new ClockExtension();
+
     private static final List<String> COMMAND_BOX_DEFAULT_STYLE = Arrays.asList("text-input", "text-field");
     private static final List<String> COMMAND_BOX_ERROR_STYLE =
             Arrays.asList("text-input", "text-field", CommandBox.ERROR_STYLE_CLASS);
@@ -137,7 +138,7 @@ protected void executeCommand(String command) {
         rememberStates();
         // Injects a fixed clock before executing a command so that the time stamp shown in the status bar
         // after each command is predictable and also different from the previous command.
-        clockRule.setInjectedClockToCurrentTime();
+        clockExtension.setInjectedClockToCurrentTime();
 
         mainWindowHandle.getCommandBox().run(command);
 
@@ -266,11 +267,11 @@ protected void assertStatusBarUnchanged() {
 
     /**
      * Asserts that only the sync status in the status bar was changed to the timing of
-     * {@code ClockRule#getInjectedClock()}, while the save location remains the same.
+     * {@code ClockExtension#getInjectedClock()}, while the save location remains the same.
      */
     protected void assertStatusBarUnchangedExceptSyncStatus() {
         StatusBarFooterHandle handle = getStatusBarFooter();
-        String timestamp = new Date(clockRule.getInjectedClock().millis()).toString();
+        String timestamp = new Date(clockExtension.getInjectedClock().millis()).toString();
         String expectedSyncStatus = String.format(SYNC_STATUS_UPDATED, timestamp);
         assertEquals(expectedSyncStatus, handle.getSyncStatus());
         assertFalse(handle.isSaveLocationChanged());

src/test/java/systemtests/ClockRule.java → src/test/java/systemtests/ClockExtension.java

@@ -4,9 +4,9 @@
 import java.time.Instant;
 import java.time.ZoneId;
 
-import org.junit.rules.TestRule;
-import org.junit.runner.Description;
-import org.junit.runners.model.Statement;
+import org.junit.jupiter.api.extension.AfterEachCallback;
+import org.junit.jupiter.api.extension.BeforeEachCallback;
+import org.junit.jupiter.api.extension.ExtensionContext;
 
 import seedu.address.ui.StatusBarFooter;
 
@@ -16,31 +16,18 @@
  * At the end of the test, the rule restores the original clock.
  * @see Clock#fixed(Instant, ZoneId)
  */
-public class ClockRule implements TestRule {
+public class ClockExtension implements BeforeEachCallback, AfterEachCallback {
     private Clock injectedClock;
     private final Clock originalClock = StatusBarFooter.getClock();
 
-    protected void before() {
-        setInjectedClockToCurrentTime();
-    }
-
-    protected void after() {
+    @Override
+    public void afterEach(ExtensionContext context) throws Exception {
         StatusBarFooter.setClock(originalClock);
     }
 
     @Override
-    public Statement apply(final Statement base, final Description description) {
-        return new Statement() {
-            @Override
-            public void evaluate() throws Throwable {
-                before();
-                try {
-                    base.evaluate();
-                } finally {
-                    after();
-                }
-            }
-        };
+    public void beforeEach(ExtensionContext context) throws Exception {
+        setInjectedClockToCurrentTime();
     }
 
     public Clock getInjectedClock() {
@@ -54,4 +41,5 @@ public void setInjectedClockToCurrentTime() {
         injectedClock = Clock.fixed(Instant.now(), ZoneId.systemDefault());
         StatusBarFooter.setClock(injectedClock);
     }
+
 }