test: Add a start for unit tests of HealthServer

Author: haphut

src/test/java/fi/hsl/common/health/HealthServerTest.java

@@ -0,0 +1,111 @@
+package fi.hsl.common.health;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.BooleanSupplier;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class HealthServerTest {
+
+    private HealthServer healthServer;
+    private final int testPort = 0;
+    private final String testEndpoint = "/healthz";
+
+    private static class CountingWrapper implements BooleanSupplier {
+
+        private final BooleanSupplier delegate;
+        private final AtomicInteger callCount = new AtomicInteger(0);
+
+        public CountingWrapper(BooleanSupplier delegate) {
+            this.delegate = delegate;
+        }
+
+        @Override
+        public boolean getAsBoolean() {
+            callCount.incrementAndGet();
+            return delegate.getAsBoolean();
+        }
+
+        public int getCallCount() {
+            return callCount.get();
+        }
+    }
+
+    @Before
+    public void setUp() throws IOException {
+        healthServer = new HealthServer(testPort, testEndpoint);
+    }
+
+    @After
+    public void tearDown() {
+        if (healthServer != null) {
+            healthServer.close();
+        }
+    }
+
+    @Test
+    public void singleUnhealthyCheckReturnsFalse() {
+        CountingWrapper unhealthyCheck = new CountingWrapper(() -> false);
+        healthServer.addCheck(unhealthyCheck);
+        boolean healthStatus = healthServer.checkHealth();
+        assertFalse(
+            "Health status should be false when one check is unhealthy.",
+            healthStatus
+        );
+        assertEquals(
+            "UnhealthyCheck should have been called once.",
+            1,
+            unhealthyCheck.getCallCount()
+        );
+    }
+
+    @Test
+    public void allHealthyChecksReturnsTrue() {
+        CountingWrapper healthyCheck1 = new CountingWrapper(() -> true);
+        CountingWrapper healthyCheck2 = new CountingWrapper(() -> true);
+        healthServer.addCheck(healthyCheck1);
+        healthServer.addCheck(healthyCheck2);
+        boolean healthStatus = healthServer.checkHealth();
+        assertTrue(
+            "Health status should be true when all checks are healthy.",
+            healthStatus
+        );
+        assertEquals(
+            "HealthyCheck1 should have been called once.",
+            1,
+            healthyCheck1.getCallCount()
+        );
+        assertEquals(
+            "HealthyCheck2 should have been called once.",
+            1,
+            healthyCheck2.getCallCount()
+        );
+    }
+
+    @Test
+    public void testCheckHealth_CheckThrowsException_ReturnsFalse() {
+        final RuntimeException testException = new RuntimeException(
+            "Simulated check failure"
+        );
+        CountingWrapper exceptionThrowingCheck = new CountingWrapper(() -> {
+            throw testException;
+        });
+        healthServer.addCheck(exceptionThrowingCheck);
+        boolean healthStatus = healthServer.checkHealth();
+        assertFalse(
+            "Health status should be false when a check throws an exception.",
+            healthStatus
+        );
+        assertEquals(
+            "ExceptionThrowingCheck should have been called once.",
+            1,
+            exceptionThrowingCheck.getCallCount()
+        );
+    }
+}