diff --git a/openai-gateway/openai-gateway-core/src/jvmTest/kotlin/com/tddworks/anthropic/api/messages/api/ContentMessageTest.kt b/openai-gateway/openai-gateway-core/src/jvmTest/kotlin/com/tddworks/anthropic/api/messages/api/ContentMessageTest.kt
new file mode 100644
index 0000000..d3e4a2b
--- /dev/null
+++ b/openai-gateway/openai-gateway-core/src/jvmTest/kotlin/com/tddworks/anthropic/api/messages/api/ContentMessageTest.kt
@@ -0,0 +1,15 @@
+package com.tddworks.anthropic.api.messages.api
+
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+
+class ContentMessageTest {
+
+    @Test
+    fun `should create a ContentMessage`() {
+        val dummyMessage = ContentMessage("Hi! My name is Claude.", "text")
+
+        assertEquals("Hi! My name is Claude.", dummyMessage.text)
+        assertEquals("text", dummyMessage.type)
+    }
+}
\ No newline at end of file
diff --git a/openai-gateway/openai-gateway-core/src/jvmTest/kotlin/com/tddworks/anthropic/api/messages/api/CreateMessageResponseTest.kt b/openai-gateway/openai-gateway-core/src/jvmTest/kotlin/com/tddworks/anthropic/api/messages/api/CreateMessageResponseTest.kt
new file mode 100644
index 0000000..55bb815
--- /dev/null
+++ b/openai-gateway/openai-gateway-core/src/jvmTest/kotlin/com/tddworks/anthropic/api/messages/api/CreateMessageResponseTest.kt
@@ -0,0 +1,24 @@
+package com.tddworks.anthropic.api.messages.api
+
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+
+
+internal class CreateMessageResponseTest {
+
+    @Test
+    fun `should create a dummy CreateMessageResponse`() {
+
+        val dummyResponse = CreateMessageResponse.dummy()
+
+        assertEquals("msg_1nZdL29xx5MUA1yADyHTEsnR8uuvGzszyY", dummyResponse.id)
+        assertEquals("claude-3-opus-20240229", dummyResponse.model)
+        assertEquals("assistant", dummyResponse.role)
+        assertNull(dummyResponse.stopReason)
+        assertNull(dummyResponse.stopSequence)
+        assertEquals("message", dummyResponse.type)
+        assertEquals(Usage(25, 1), dummyResponse.usage)
+        assertEquals(listOf(ContentMessage("Hi! My name is Claude.", "text")), dummyResponse.content)
+    }
+
+}
\ No newline at end of file
diff --git a/openai-gateway/openai-gateway-core/src/jvmTest/kotlin/com/tddworks/anthropic/api/messages/api/DeltaTest.kt b/openai-gateway/openai-gateway-core/src/jvmTest/kotlin/com/tddworks/anthropic/api/messages/api/DeltaTest.kt
new file mode 100644
index 0000000..758d1f0
--- /dev/null
+++ b/openai-gateway/openai-gateway-core/src/jvmTest/kotlin/com/tddworks/anthropic/api/messages/api/DeltaTest.kt
@@ -0,0 +1,19 @@
+package com.tddworks.anthropic.api.messages.api
+
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+
+
+class DeltaTest {
+
+    @Test
+    fun `should create dummy Delta`() {
+        val delta = Delta.dummy()
+        assertEquals("text_delta", delta.type)
+        assertEquals("Hello", delta.text)
+        assertEquals("end_turn", delta.stopReason)
+        assertEquals(null, delta.stopSequence)
+        assertEquals(Usage(outputTokens = 15), delta.usage)
+    }
+
+}
\ No newline at end of file
diff --git a/openai-gateway/openai-gateway-core/src/jvmTest/kotlin/com/tddworks/anthropic/api/messages/api/UsageTest.kt b/openai-gateway/openai-gateway-core/src/jvmTest/kotlin/com/tddworks/anthropic/api/messages/api/UsageTest.kt
new file mode 100644
index 0000000..3ffe821
--- /dev/null
+++ b/openai-gateway/openai-gateway-core/src/jvmTest/kotlin/com/tddworks/anthropic/api/messages/api/UsageTest.kt
@@ -0,0 +1,35 @@
+package com.tddworks.anthropic.api.messages.api
+
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class UsageTest {
+    @Test
+    fun `should create a empty Usage`() {
+        val usage = Usage()
+        val json = Json.encodeToString(usage)
+
+        val expectedJson = "{}"
+        assertEquals(expectedJson, json)
+    }
+
+    @Test
+    fun `should create a dummy Usage`() {
+        val usage = Usage(inputTokens = 10, outputTokens = 20)
+        val json = Json.encodeToString(usage)
+
+        val expectedJson = "{\"input_tokens\":10,\"output_tokens\":20}"
+        assertEquals(expectedJson, json)
+    }
+
+    @Test
+    fun `should parse a Usage from json`() {
+        val json = "{\"input_tokens\":5,\"output_tokens\":15}"
+        val usage = Json.decodeFromString<Usage>(json)
+
+        assertEquals(5, usage.inputTokens)
+        assertEquals(15, usage.outputTokens)
+    }
+}
\ No newline at end of file