test: Direct unit tests for ClasspathResourceHandler

Author: thced

src/test/java/com/retailsvc/http/internal/ClasspathResourceHandlerTest.java

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+package com.retailsvc.http.internal;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.ArgumentMatchers.longThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import com.sun.net.httpserver.Headers;
+import com.sun.net.httpserver.HttpExchange;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import org.junit.jupiter.api.Test;
+
+class ClasspathResourceHandlerTest {
+
+  @Test
+  void getServesBytesVerbatim() throws IOException {
+    byte[] expected = readResource("/sample.txt");
+    HttpExchange ex = newExchange("GET");
+    ByteArrayOutputStream body = new ByteArrayOutputStream();
+    when(ex.getResponseBody()).thenReturn(body);
+
+    new ClasspathResourceHandler("/sample.txt").handle(ex);
+
+    verify(ex).sendResponseHeaders(eq(200), eq((long) expected.length));
+    assertThat(body.toByteArray()).isEqualTo(expected);
+  }
+
+  @Test
+  void headSendsContentLengthHeaderWithoutBody() throws IOException {
+    byte[] expected = readResource("/sample.txt");
+    HttpExchange ex = newExchange("HEAD");
+    Headers responseHeaders = new Headers();
+    when(ex.getResponseHeaders()).thenReturn(responseHeaders);
+
+    new ClasspathResourceHandler("/sample.txt").handle(ex);
+
+    verify(ex).sendResponseHeaders(eq(200), eq(-1L));
+    assertThat(responseHeaders.getFirst("Content-Length"))
+        .isEqualTo(String.valueOf(expected.length));
+  }
+
+  @Test
+  void infersApplicationJsonForJsonExtension() throws IOException {
+    assertThat(contentTypeFor("/openapi.json")).isEqualTo("application/json");
+  }
+
+  @Test
+  void infersApplicationYamlForYamlExtension() throws IOException {
+    assertThat(contentTypeFor("/openapi.yaml")).isEqualTo("application/yaml");
+  }
+
+  @Test
+  void infersTextPlainForTxtExtension() throws IOException {
+    assertThat(contentTypeFor("/sample.txt")).isEqualTo("text/plain; charset=utf-8");
+  }
+
+  @Test
+  void fallsBackToOctetStreamForUnknownExtension() throws IOException {
+    assertThat(contentTypeFor("/sample.bin")).isEqualTo("application/octet-stream");
+  }
+
+  @Test
+  void missingResourceThrowsIllegalArgumentExceptionWithPathInMessage() {
+    assertThatThrownBy(() -> new ClasspathResourceHandler("/does-not-exist.json"))
+        .isInstanceOf(IllegalArgumentException.class)
+        .hasMessageContaining("/does-not-exist.json");
+  }
+
+  @Test
+  void resourceIsLoadedEagerlyAtConstruction() {
+    // If the resource were loaded lazily, construction would succeed and the handle()
+    // call would fail. Construction itself must fail.
+    assertThatThrownBy(() -> new ClasspathResourceHandler("/missing.txt"))
+        .isInstanceOf(IllegalArgumentException.class);
+  }
+
+  @Test
+  void contentLengthIsSetForGetRequests() throws IOException {
+    HttpExchange ex = newExchange("GET");
+    when(ex.getResponseBody()).thenReturn(new ByteArrayOutputStream());
+
+    new ClasspathResourceHandler("/sample.txt").handle(ex);
+
+    verify(ex).sendResponseHeaders(eq(200), longThat(n -> n > 0));
+  }
+
+  private static String contentTypeFor(String resource) throws IOException {
+    HttpExchange ex = newExchange("GET");
+    Headers headers = new Headers();
+    when(ex.getResponseHeaders()).thenReturn(headers);
+    when(ex.getResponseBody()).thenReturn(new ByteArrayOutputStream());
+    new ClasspathResourceHandler(resource).handle(ex);
+    return headers.getFirst("Content-Type");
+  }
+
+  private static HttpExchange newExchange(String method) {
+    HttpExchange ex = mock(HttpExchange.class);
+    when(ex.getRequestMethod()).thenReturn(method);
+    when(ex.getResponseHeaders()).thenReturn(new Headers());
+    return ex;
+  }
+
+  private static byte[] readResource(String path) throws IOException {
+    try (InputStream in = ClasspathResourceHandlerTest.class.getResourceAsStream(path)) {
+      if (in == null) {
+        throw new IOException("missing fixture: " + path);
+      }
+      return in.readAllBytes();
+    }
+  }
+}

src/test/resources/sample.bin

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+binary-payload

src/test/resources/sample.txt

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+hello text