java: add stub time

Author: l-lin

java/data-structures/pom.xml

@@ -12,8 +12,8 @@
     <artifactId>data-structures</artifactId>
 
     <properties>
-        <assertj.version>3.26.0</assertj.version>
-        <junit.version>5.10.2</junit.version>
+        <assertj.version>3.27.3</assertj.version>
+        <junit.version>5.11.4</junit.version>
     </properties>
 
     <dependencyManagement>

java/data-structures/src/test/java/lin/louis/data_structures/time/TimeHelper.java

@@ -0,0 +1,40 @@
+package lin.louis.data_structures.time;
+
+import java.time.Clock;
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+
+/**
+ * The Java API, such as {@link LocalDateTime#now()}, {@link Instant#now()}, or {@link Clock#systemUTC()}, can be
+ * difficult to stub because they are closely coupled with one another. Stubbing one can be quite challenging.
+ * While we can use <a href="https://www.baeldung.com/mockito-mock-static-methods">Mockito static methods</a>,
+ * some libraries use one of the three above (or any variant with some parameters), which might generate
+ * unexpected behavior in your tests or, even worse, cause flaky tests.
+ * <br/>
+ * One option is to create a helper that your code MUST use to get the current date and time instead of using
+ * the Java ones. This way, it's easier to stub and does not impact the behavior of the libraries.
+ * <br/>
+ * However, the drawback is that you need to use this specific helper in your code, and if you expect some
+ * specific behavior from the libraries based on the current time, this option won't work.
+ */
+public class TimeHelper {
+
+    /**
+     * No setter is exposed to ensure that only tests using {@link TimeTraveler} can set the value of the thread-local
+     * variable via reflection. This prevents the implementation code from accidentally modifying the current time.
+     */
+    private static final ThreadLocal<LocalDateTime> NOW = new ThreadLocal<>();
+
+    public static LocalDateTime nowUTC() {
+        var now = NOW.get();
+        return now != null ? now : LocalDateTime.now(ZoneOffset.UTC);
+    }
+
+    public static LocalDate todayUTC() {
+        return nowUTC().toLocalDate();
+    }
+
+    private TimeHelper() {}
+}

java/data-structures/src/test/java/lin/louis/data_structures/time/TimeHelperTest.java

@@ -0,0 +1,27 @@
+package lin.louis.data_structures.time;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.time.LocalDateTime;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+class TimeHelperTest {
+    private static final LocalDateTime NOW = LocalDateTime.parse("2025-02-09T18:30:31");
+
+    @RegisterExtension
+    private static TimeTraveler TIME_TRAVELER = TimeTraveler.travelTo(NOW);
+
+    @Test
+    void currentTimeHasBeenStubbed() {
+        var actual = TimeHelper.nowUTC();
+
+        assertThat(actual).isEqualTo(NOW);
+    }
+
+    @Test
+    void currentTimeCanBeInjected(LocalDateTime now) {
+        assertThat(now).isEqualTo(NOW);
+    }
+}

java/data-structures/src/test/java/lin/louis/data_structures/time/TimeTraveler.java

@@ -0,0 +1,62 @@
+package lin.louis.data_structures.time;
+
+import java.time.LocalDateTime;
+
+import org.junit.jupiter.api.extension.AfterAllCallback;
+import org.junit.jupiter.api.extension.BeforeAllCallback;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.api.extension.ParameterContext;
+import org.junit.jupiter.api.extension.ParameterResolutionException;
+import org.junit.jupiter.api.extension.ParameterResolver;
+
+public class TimeTraveler implements BeforeAllCallback, AfterAllCallback, ParameterResolver {
+
+    private final LocalDateTime now;
+
+    /**
+     * Represents the level for which the tests are located. We need to track it
+     * because we can have multiple nested tests.
+     */
+    private int testLevel;
+
+    public static TimeTraveler travelTo(LocalDateTime dateTime) {
+        return new TimeTraveler(dateTime);
+    }
+
+    private TimeTraveler(LocalDateTime now) {
+        this.now = now;
+    }
+
+    @Override
+    public void beforeAll(ExtensionContext context) throws Exception {
+        timeKeeperThreadLocal().set(now);
+        testLevel++;
+    }
+
+    @Override
+    public void afterAll(ExtensionContext context) throws Exception {
+        testLevel--;
+        if (testLevel == 0) {
+            timeKeeperThreadLocal().remove();
+        }
+    }
+
+    @Override
+    public boolean supportsParameter(ParameterContext parameterContext, ExtensionContext extensionContext)
+            throws ParameterResolutionException {
+        return parameterContext.getParameter().getType() == LocalDateTime.class;
+    }
+
+    @Override
+    public Object resolveParameter(ParameterContext parameterContext, ExtensionContext extensionContext)
+            throws ParameterResolutionException {
+        return now;
+    }
+
+    @SuppressWarnings("unchecked")
+    private ThreadLocal<LocalDateTime> timeKeeperThreadLocal() throws NoSuchFieldException, IllegalAccessException {
+        var nowField = TimeHelper.class.getDeclaredField("NOW");
+        nowField.setAccessible(true);
+        return (ThreadLocal<LocalDateTime>) nowField.get(null);
+    }
+}

java/security/src/main/java/lin/louis/security/sign/X509Certificates.java

@@ -2,5 +2,5 @@
 
 public class X509Certificates {
     public static final String PRIVATE_KEY = "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";
-    public static final String PUBLIC_KEY = 	   		"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";
+    public static final String PUBLIC_KEY = "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";
 }