Add NamingConventionTest (#3814)

* verify some behaviors of the NamingConvention class.

* document that system property hyphens and underscores don't actually normalize the same

* spotless

instrumentation-api/src/test/java/io/opentelemetry/instrumentation/api/config/NamingConventionTest.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.api.config;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class NamingConventionTest {
+
+  @Test
+  void normalizeEnvWithHyphen() {
+    // Unlikely that the environment can contain a name like this, but let's doc the behavior
+    String result = NamingConvention.ENV_VAR.normalize("FOO_BAR-BAZ");
+    assertEquals("foo.bar-baz", result);
+  }
+
+  @Test
+  void systemPropertyWithHyphen() {
+    // Normalizes to the same thing
+    String result1 =
+        NamingConvention.ENV_VAR.normalize(
+            "OTEL_INSTRUMENTATION_COMMON_DB_STATEMENT_SANITIZER_ENABLED");
+    String result2 =
+        NamingConvention.DOT.normalize(
+            "otel.instrumentation.common.db-statement-sanitizer.enabled");
+    assertEquals("otel.instrumentation.common.db.statement.sanitizer.enabled", result1);
+    assertEquals("otel.instrumentation.common.db.statement.sanitizer.enabled", result2);
+  }
+
+  @Test
+  void hyphensAndUnderscoresDoNotNormalizeTheSame() {
+    String result1 = NamingConvention.DOT.normalize("otel.something_else_entirely.foobar");
+    assertEquals("otel.something_else_entirely.foobar", result1);
+
+    String result2 = NamingConvention.DOT.normalize("otel.something-else-entirely.foobar");
+    assertEquals("otel.something.else.entirely.foobar", result2);
+  }
+}