Hoist up Node Gradle plugin, set TestTomcat baseDir, add hasContentType matcher, HTTP status consts

settings.gradle.kts

@@ -8,6 +8,7 @@
 plugins {
     // Apply the foojay-resolver plugin to allow automatic download of JDKs
     id("org.gradle.toolchains.foojay-resolver-convention") version "0.7.0"
+    id("com.github.node-gradle.node") version "7.0.1" apply false
     id("com.github.ben-manes.versions") version "0.50.0" apply false
 }
 

strcalc/build.gradle.kts

@@ -8,7 +8,7 @@ import com.github.benmanes.gradle.versions.updates.DependencyUpdatesTask
 plugins {
     war
     jacoco
-    id("com.github.node-gradle.node") version "7.0.1"
+    id("com.github.node-gradle.node")
     id("com.github.ben-manes.versions")
 }
 

strcalc/src/test/java/com/mike_bland/training/testing/matchers/HasContentType.java

@@ -0,0 +1,40 @@
+package com.mike_bland.training.testing.matchers;
+
+import org.hamcrest.Description;
+import org.hamcrest.TypeSafeMatcher;
+
+import java.net.http.HttpResponse;
+
+// Custom Hamcrest matcher validating the Content-Type header of a HttpResponse.
+//
+// This could be generalized to check any HTTP header, or collection thereof.
+// However, since this is a teaching example, we'll keep it straightforward.
+class HasContentType<T> extends TypeSafeMatcher<HttpResponse<T>> {
+    private final String expected;
+
+    // Constructor to register the expected Content-Type value.
+    HasContentType(String contentType) {
+        this.expected = contentType;
+    }
+
+    // Helper method to extract the Content-Type value from an HttpResponse.
+    private String getContentType(HttpResponse<T> resp) {
+        return resp.headers().firstValue("Content-Type").orElse("");
+    }
+
+    // Performs the actual assertion.
+    @Override public boolean matchesSafely(HttpResponse<T> resp) {
+        return getContentType(resp).equals(expected);
+    }
+
+    // Describes the "Expected:" value in assertion failure messages.
+    @Override public void describeTo(Description description) {
+        description.appendText(expected);
+    }
+
+    // Describes the actual ("but:") value in assertion failure messages.
+    @Override public void describeMismatchSafely(
+            HttpResponse<T> resp, Description description) {
+        description.appendText(getContentType(resp));
+    }
+}

strcalc/src/test/java/com/mike_bland/training/testing/matchers/Matchers.java

@@ -0,0 +1,23 @@
+package com.mike_bland.training.testing.matchers;
+
+import org.hamcrest.Matcher;
+
+import java.net.http.HttpResponse;
+
+// Collection of custom Hamcrest Matcher<T> classes for assertThat() statements.
+//
+// These tutorials describe how to write Matchers:
+//
+// - https://hamcrest.org/JavaHamcrest/tutorial
+// - https://www.baeldung.com/hamcrest-custom-matchers
+//
+// Note that these tutorials show the static factory functions defined on the
+// same class as the Matcher. However, Hamcrest itself collects these factories
+// into its own org.hamcrest.Matchers class for convenience, instead of
+// importing one class per Matcher.
+public class Matchers {
+    public static <T> Matcher<HttpResponse<T>> hasContentType(
+            String contentType) {
+        return new HasContentType<>(contentType);
+    }
+}

strcalc/src/test/java/com/mike_bland/training/testing/stringcalculator/ServletContractTest.java

@@ -10,6 +10,7 @@
 import com.mike_bland.training.testing.annotations.MediumTest;
 import com.mike_bland.training.testing.utils.PortPicker;
 import com.mike_bland.training.testing.utils.TestTomcat;
+import jakarta.servlet.http.HttpServletResponse;
 import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.BeforeAll;
 
@@ -20,6 +21,7 @@
 import java.net.http.HttpResponse.BodyHandlers;
 import java.util.Optional;
 
+import static com.mike_bland.training.testing.matchers.Matchers.hasContentType;
 import static com.mike_bland.training.testing.stringcalculator.Servlet.DEFAULT_ROOT;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.containsString;
@@ -65,11 +67,8 @@ void servesCorrectLandingPage() throws Exception {
 
         var resp = sendRequest(req);
 
-        assertEquals(200, resp.statusCode());
-        assertEquals(
-                Optional.of("text/html"),
-                resp.headers().firstValue("Content-Type")
-        );
+        assertEquals(HttpServletResponse.SC_OK, resp.statusCode());
+        assertThat(resp, hasContentType("text/html"));
         assertThat(
                 resp.body(),
                 containsString("<title>String Calculator - ")
@@ -86,11 +85,8 @@ void addEndpointPlaceholder() throws Exception {
 
         var resp = sendRequest(req);
 
-        assertEquals(200, resp.statusCode());
-        assertEquals(
-                Optional.of("text/plain;charset=UTF-8"),
-                resp.headers().firstValue("Content-Type")
-        );
+        assertEquals(HttpServletResponse.SC_OK, resp.statusCode());
+        assertThat(resp, hasContentType("text/plain;charset=UTF-8"));
         assertEquals("placeholder for /add API endpoint", resp.body());
     }
 }

strcalc/src/test/java/com/mike_bland/training/testing/utils/TestTomcat.java

@@ -42,6 +42,7 @@ public class TestTomcat {
     private final int port;
     private final String contextPath;
     private final URI uri;
+    private final File baseDir;
     private Tomcat tomcat;
     private boolean running;
 
@@ -52,12 +53,14 @@ public TestTomcat(int port, String contextPath)
         this.uri = URI.create(
                 String.format("http://localhost:%d%s", port, contextPath)
         );
+        this.baseDir = new File("build/test-tomcat-basedir");
     }
 
     public synchronized void start() throws LifecycleException {
         if (running) return;
         running = true;
         tomcat = new Tomcat();
+        tomcat.setBaseDir(this.baseDir.getAbsolutePath());
         tomcat.setPort(port);
         tomcat.setSilent(true);
 
@@ -127,7 +130,7 @@ public synchronized void stop() throws LifecycleException, IOException {
         if (!running) return;
         running = false;
         tomcat.stop();
-        deleteBaseDir(port);
+        deleteBaseDir(this.baseDir);
     }
 
     private static String validateContextPath(String contextPath)
@@ -141,10 +144,7 @@ private static String validateContextPath(String contextPath)
         return contextPath;
     }
 
-    private static void deleteBaseDir(int port) throws IOException {
-        // The Tomcat.setBaseDir() documentation explains the base dir schema:
-        // - https://tomcat.apache.org/tomcat-10.1-doc/api/org/apache/catalina/startup/Tomcat.html#setBaseDir(java.lang.String)
-        final var baseDir = new File("tomcat.%d".formatted(port));
+    private static void deleteBaseDir(File baseDir) throws IOException {
         List<String> failed;
 
         try (var fileStream = Files.walk(baseDir.toPath())) {