feat: Add HealthOutcome record for health responses

Author: thced

src/main/java/com/retailsvc/http/HealthOutcome.java

@@ -0,0 +1,27 @@
+package com.retailsvc.http;
+
+import java.util.List;
+import java.util.Objects;
+
+/**
+ * Wire-shape carrier for the {@link Handlers#healthHandler health handler} response.
+ *
+ * <p>The record owns the JSON shape on the wire — {@code {"outcome": "...", "dependencies": [
+ * {"id": "...", "status": "..."} ]}}. Construct it from whatever check-running mechanism the caller
+ * prefers; this library has no opinion.
+ *
+ * @param outcome overall outcome; {@code "Up"} (case-insensitive) means healthy
+ * @param dependencies per-dependency statuses; {@code null} is normalised to an empty list
+ */
+public record HealthOutcome(String outcome, List<Dependency> dependencies) {
+
+  public HealthOutcome {
+    Objects.requireNonNull(outcome, "outcome");
+    dependencies = List.copyOf(Objects.requireNonNullElse(dependencies, List.of()));
+  }
+
+  /** Returns {@code true} when {@link #outcome()} equals {@code "Up"} ignoring case. */
+  public boolean isUp() {
+    return "Up".equalsIgnoreCase(outcome);
+  }
+}

src/test/java/com/retailsvc/http/HealthOutcomeTest.java

@@ -0,0 +1,54 @@
+package com.retailsvc.http;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatNullPointerException;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+class HealthOutcomeTest {
+
+  @Test
+  void exposesOutcomeAndDependencies() {
+    HealthOutcome o = new HealthOutcome("Up", List.of(new Dependency("jdbc", "Up")));
+    assertThat(o.outcome()).isEqualTo("Up");
+    assertThat(o.dependencies()).containsExactly(new Dependency("jdbc", "Up"));
+  }
+
+  @Test
+  void rejectsNullOutcome() {
+    assertThatNullPointerException()
+        .isThrownBy(() -> new HealthOutcome(null, List.of()))
+        .withMessageContaining("outcome");
+  }
+
+  @Test
+  void coercesNullDependenciesToEmpty() {
+    HealthOutcome o = new HealthOutcome("Up", null);
+    assertThat(o.dependencies()).isEmpty();
+  }
+
+  @Test
+  void copiesDependencyListDefensively() {
+    List<Dependency> mutable = new ArrayList<>();
+    mutable.add(new Dependency("jdbc", "Up"));
+    HealthOutcome o = new HealthOutcome("Up", mutable);
+    mutable.clear();
+    assertThat(o.dependencies()).hasSize(1);
+  }
+
+  @Test
+  void isUpReturnsTrueForUpCaseInsensitive() {
+    assertThat(new HealthOutcome("Up", List.of()).isUp()).isTrue();
+    assertThat(new HealthOutcome("UP", List.of()).isUp()).isTrue();
+    assertThat(new HealthOutcome("up", List.of()).isUp()).isTrue();
+  }
+
+  @Test
+  void isUpReturnsFalseForAnythingElse() {
+    assertThat(new HealthOutcome("Down", List.of()).isUp()).isFalse();
+    assertThat(new HealthOutcome("", List.of()).isUp()).isFalse();
+    assertThat(new HealthOutcome("Degraded", List.of()).isUp()).isFalse();
+  }
+}