Coding style: simplify assertions (open-telemetry#17418)

Author: trask

.github/agents/code-review-and-fix.agent.md

@@ -142,6 +142,8 @@ Auto-fix boundaries:
     lambdas where the lambda parameter is already an `AbstractAssert` (e.g.,
     `AbstractStringAssert`). Calls like `taskId.contains(jobName)` on the assert object are
     already valid AssertJ assertions; do not wrap them in `assertThat(...).isTrue()`
+  - AssertJ `.as(...)` descriptions and `.withFailMessage(...)` in tests — remove them
+    and prefer direct assertions whose failure output already exposes the unexpected values
   - deterministic semconv constant handling aligned with repository rules
   - missing test-task wiring patterns with clear canonical form
   - missing `testInstrumentation` cross-version references — when a javaagent module belongs

.github/agents/knowledge/testing-general-patterns.md

@@ -9,6 +9,8 @@
 
 - JUnit 5, AssertJ assertions (not JUnit `assertEquals`/`assertTrue`).
 - Test classes and methods should be package-private (no `public`).
+- Do not use AssertJ `.as(...)` descriptions or `.withFailMessage(...)` in tests.
+  Prefer direct assertions whose failure output shows the unexpected values.
 
 ## Test Resource Cleanup
 

instrumentation/c3p0-0.9/testing/src/main/java/io/opentelemetry/instrumentation/c3p0/AbstractC3p0InstrumentationTest.java

@@ -80,9 +80,7 @@ void shouldReportMetrics() throws Exception {
   private void assertDataSourceMetrics(PooledDataSource dataSource) {
     String dataSourceName = dataSource.getDataSourceName();
 
-    assertThat(dataSourceName)
-        .as("c3p0 generates a unique pool name if it's not explicitly provided")
-        .isNotEmpty();
+    assertThat(dataSourceName).isNotEmpty();
 
     DbConnectionPoolMetricsAssertions.create(
             testing(), INSTRUMENTATION_NAME, dataSource.getDataSourceName())

instrumentation/jetty-httpclient/jetty-httpclient-9.2/library/src/test/java/io/opentelemetry/instrumentation/jetty/httpclient/v9_2/JettyHttpClient9HttpCallTest.java

@@ -101,11 +101,7 @@ void inputStreamListenerBodyIsDelivered() throws Exception {
       body = buf.toByteArray();
     }
 
-    assertThat(body)
-        .as(
-            "Response body must not be empty — if it is, the OTel proxy is missing "
-                + "DemandedContentListener and Jetty filters it out before delivering content")
-        .isNotEmpty();
+    assertThat(body).isNotEmpty();
     assertThat(new String(body, UTF_8)).isEqualTo(EXPECTED_BODY);
   }
 }

instrumentation/oshi/library/src/test/java/io/opentelemetry/instrumentation/oshi/ProcessMetricsTest.java

@@ -45,6 +45,6 @@ protected InstrumentationExtension testing() {
 
   @Test
   void verifyObservablesAreNotEmpty() {
-    assertThat(observables).as("List of observables").isNotEmpty();
+    assertThat(observables).isNotEmpty();
   }
 }

instrumentation/oshi/library/src/test/java/io/opentelemetry/instrumentation/oshi/SystemMetricsTest.java

@@ -45,6 +45,6 @@ protected InstrumentationExtension testing() {
 
   @Test
   void verifyObservablesAreNotEmpty() {
-    assertThat(observables).as("List of observables").isNotEmpty();
+    assertThat(observables).isNotEmpty();
   }
 }

instrumentation/servlet/servlet-5.0/tomcat-testing/src/test/java/io/opentelemetry/javaagent/instrumentation/servlet/v5_0/tomcat/TomcatServlet5WebXmlFilterTest.java

@@ -137,7 +137,7 @@ private static void copyClassFile(Class<?> clazz, File targetDir) throws Excepti
     String classFileName = clazz.getSimpleName() + ".class";
     String classResourcePath = clazz.getName().replace('.', '/') + ".class";
     try (InputStream is = clazz.getClassLoader().getResourceAsStream(classResourcePath)) {
-      assertThat(is).as("Class file resource for " + clazz.getName()).isNotNull();
+      assertThat(is).isNotNull();
       Files.copy(
           is, new File(targetDir, classFileName).toPath(), StandardCopyOption.REPLACE_EXISTING);
     }

instrumentation/tomcat/tomcat-jdbc/javaagent/src/test/java/io/opentelemetry/javaagent/instrumentation/tomcat/jdbc/TomcatJdbcInstrumentationTest.java

@@ -62,9 +62,7 @@ void shouldReportMetrics() throws Exception {
   }
 
   private static void assertConnectionPoolMetrics(String poolName) {
-    assertThat(poolName)
-        .as("tomcat-jdbc generates a unique pool name if it's not explicitly provided")
-        .isNotEmpty();
+    assertThat(poolName).isNotEmpty();
 
     DbConnectionPoolMetricsAssertions.create(testing, "io.opentelemetry.tomcat-jdbc", poolName)
         // no timeouts happen during this test

javaagent-internal-logging-application/src/test/java/io/opentelemetry/javaagent/logging/application/ConcurrentIntegrationTest.java

@@ -56,9 +56,7 @@ void shouldLogEverything() throws InterruptedException {
 
     futures.forEach(f -> f.cancel(true));
 
-    assertThat(logMessages)
-        .as("Verify that the application logger bridge did not lose any messages")
-        .hasSize(count.get());
+    assertThat(logMessages).hasSize(count.get());
   }
 
   private static final class TestLogger implements InternalLogger {

javaagent/src/test/java/io/opentelemetry/javaagent/ShadingTest.java

@@ -47,11 +47,7 @@ void agentJarContainsOnlyExpectedEntries() throws Exception {
               });
     }
 
-    assertThat(unexpectedEntries)
-        .as(
-            "Agent jar should only contain entries with expected prefixes: %s",
-            EXPECTED_ENTRY_PREFIXES)
-        .isEmpty();
+    assertThat(unexpectedEntries).isEmpty();
   }
 
   private static String getAgentJarPath() {