Add tests for DistroComponentProvider.addDistroResourceProvider

Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>

Author: zeitlinger

custom/src/test/java/com/grafana/extensions/resources/internal/DistroComponentProviderTest.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright Grafana Labs
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.grafana.extensions.resources.internal;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import io.opentelemetry.sdk.extension.incubator.fileconfig.internal.model.ExperimentalResourceDetectorModel;
+import io.opentelemetry.sdk.extension.incubator.fileconfig.internal.model.OpenTelemetryConfigurationModel;
+import org.junit.jupiter.api.Test;
+
+class DistroComponentProviderTest {
+
+  @Test
+  void addsDetectorWhenAbsent() {
+    OpenTelemetryConfigurationModel model = new OpenTelemetryConfigurationModel();
+
+    DistroComponentProvider.addDistroResourceProvider(model);
+
+    assertThat(model.getResource().getDetectionDevelopment().getDetectors())
+        .hasSize(1)
+        .first()
+        .satisfies(
+            d ->
+                assertThat(d.getAdditionalProperties())
+                    .containsKey(DistroComponentProvider.GRAFANA_JAVAAGENT_DISTRIBUTION));
+  }
+
+  @Test
+  void doesNotDuplicateWhenPresent() {
+    OpenTelemetryConfigurationModel model = new OpenTelemetryConfigurationModel();
+    DistroComponentProvider.addDistroResourceProvider(model);
+    DistroComponentProvider.addDistroResourceProvider(model);
+
+    assertThat(model.getResource().getDetectionDevelopment().getDetectors()).hasSize(1);
+  }
+
+  @Test
+  void preservesExistingDetectors() {
+    OpenTelemetryConfigurationModel model = new OpenTelemetryConfigurationModel();
+    DistroComponentProvider.addDistroResourceProvider(model);
+
+    // Add another detector
+    ExperimentalResourceDetectorModel other = new ExperimentalResourceDetectorModel();
+    other.getAdditionalProperties().put("other-detector", null);
+    model.getResource().getDetectionDevelopment().getDetectors().add(other);
+
+    DistroComponentProvider.addDistroResourceProvider(model);
+
+    assertThat(model.getResource().getDetectionDevelopment().getDetectors()).hasSize(2);
+  }
+}