diff --git a/generativeai/build.gradle.kts b/generativeai/build.gradle.kts
index ba88cefb..7a8dfebd 100644
--- a/generativeai/build.gradle.kts
+++ b/generativeai/build.gradle.kts
@@ -89,6 +89,7 @@ dependencies {
     testImplementation("io.kotest:kotest-assertions-core:5.5.5")
     testImplementation("io.kotest:kotest-assertions-core-jvm:5.5.5")
     testImplementation("io.mockk:mockk:1.12.8")
+    testImplementation("org.json:json:20240303")
     androidTestImplementation("androidx.test.ext:junit:1.1.5")
     androidTestImplementation("androidx.test.espresso:espresso-core:3.5.1")
 
diff --git a/generativeai/src/test/java/com/google/ai/client/generativeai/FunctionCallingTests.kt b/generativeai/src/test/java/com/google/ai/client/generativeai/FunctionCallingTests.kt
new file mode 100644
index 00000000..0f862fe5
--- /dev/null
+++ b/generativeai/src/test/java/com/google/ai/client/generativeai/FunctionCallingTests.kt
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.ai.client.generativeai
+
+import com.google.ai.client.generativeai.type.FunctionCallPart
+import com.google.ai.client.generativeai.type.Schema
+import com.google.ai.client.generativeai.type.Tool
+import com.google.ai.client.generativeai.type.defineFunction
+import io.kotest.assertions.throwables.shouldThrowWithMessage
+import io.kotest.matchers.shouldBe
+import org.json.JSONObject
+import org.junit.Test
+
+internal class FunctionCallingTests {
+
+  @Test
+  fun `function calls with valid args should succeed`() = doBlocking {
+    val functionDeclaration =
+      defineFunction(
+        "name",
+        "description",
+        Schema.str("param1", "description"),
+        Schema.num("param2", "description"),
+        Schema.bool("param3", "description"),
+        Schema.int("param4", "description"),
+      ) { param1, param2, param3, param4 ->
+        JSONObject(mapOf("result" to "success"))
+      }
+    val model = GenerativeModel("model", "key", tools = listOf(Tool(listOf(functionDeclaration))))
+
+    val functionCall =
+      FunctionCallPart(
+        "name",
+        mapOf(
+          ("param1" to "valid parameter"),
+          ("param2" to "2.2"),
+          ("param3" to "false"),
+          ("param4" to "2"),
+        ),
+      )
+
+    val result = model.executeFunction(functionCall)
+
+    result["result"] shouldBe "success"
+  }
+
+  @Test
+  fun `function calls with invalid args should fail`() = doBlocking {
+    val functionDeclaration =
+      defineFunction("name", "description", Schema.str("param1", "description")) { param1 ->
+        JSONObject(mapOf("result" to "success"))
+      }
+    val model = GenerativeModel("model", "key", tools = listOf(Tool(listOf(functionDeclaration))))
+
+    val functionCall = FunctionCallPart("name", mapOf("param1" to null))
+
+    shouldThrowWithMessage<RuntimeException>(
+      "Missing argument for parameter \"param1\" for function \"name\""
+    ) {
+      model.executeFunction(functionCall)
+    }
+  }
+}