Revamped Mongo comment tests

Author: Yoone

dd-java-agent/instrumentation/mongo/driver-4.0/src/test/groovy/MongoDBMCommentTest.groovy

@@ -0,0 +1,51 @@
+import datadog.trace.core.database.SharedDBCommenter
+import spock.lang.Specification
+
+class MongoDBMCommentTest extends Specification {
+  def "SharedDBCommenter builds MongoDB comment correctly"() {
+    when:
+    String comment = SharedDBCommenter.buildComment(
+      "test-mongo-service",
+      "mongo",
+      "localhost",
+      "testdb",
+      "00-1234567890abcdef1234567890abcdef-1234567890abcdef-01"
+      )
+
+    then:
+    comment != null
+    comment.contains("ddps='")
+    comment.contains("dddbs='test-mongo-service'")
+    comment.contains("ddh='localhost'")
+    comment.contains("dddb='testdb'")
+    comment.contains("traceparent='00-1234567890abcdef1234567890abcdef-1234567890abcdef-01'")
+  }
+
+  def "SharedDBCommenter detects existing trace comments"() {
+    given:
+    String existingComment = "ddps='service1',dddbs='mongo-service',ddh='host'"
+
+    expect:
+    SharedDBCommenter.containsTraceComment(existingComment) == true
+    SharedDBCommenter.containsTraceComment("some other comment") == false
+    SharedDBCommenter.containsTraceComment("") == false
+  }
+
+  def "SharedDBCommenter with valid values produces expected comment format"() {
+    when:
+    String comment = SharedDBCommenter.buildComment(
+      "test-service",
+      "mongo",
+      "test-host",
+      "test-db",
+      "00-test-trace-test-span-01"
+      )
+
+    then:
+    comment != null
+    comment.contains("dddbs='test-service'")
+    comment.contains("ddh='test-host'")
+    comment.contains("dddb='test-db'")
+    comment.contains("traceparent='00-test-trace-test-span-01'")
+  }
+}