diff --git a/Cargo.toml b/Cargo.toml
index d4ae59e..a2289ea 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,14 +5,16 @@ edition = "2021"
 build = "build.rs"
 
 [dependencies]
-prost = "0.11.9"
+prost = "0.11.6"
 reqwest = { version = "0.11.13", features = ["rustls-tls"] }
 
-[dev-dependencies]
-
 [build-dependencies]
 prost-build = { version = "0.11.3" }
 reqwest =  { version = "0.11.13", features = ["blocking"] }
 
+[dev-dependencies]
+mockito = "0.31.1"
+tokio = { version = "1.22.0", features = ["macros"]}
+
 [features]
 genproto = []
diff --git a/tests/tests.rs b/tests/tests.rs
new file mode 100644
index 0000000..af26256
--- /dev/null
+++ b/tests/tests.rs
@@ -0,0 +1,291 @@
+#[cfg(test)]
+mod tests {
+	use mockito::{self, Matcher};
+	use prost::Message;
+	use vss_client::client::VssClient;
+	use vss_client::error::VssError;
+
+	use vss_client::types::{
+		ErrorCode, ErrorResponse, GetObjectRequest, GetObjectResponse, KeyValue, ListKeyVersionsRequest,
+		ListKeyVersionsResponse, PutObjectRequest, PutObjectResponse,
+	};
+
+	const GET_OBJECT_ENDPOINT: &'static str = "/getObject";
+	const PUT_OBJECT_ENDPOINT: &'static str = "/putObjects";
+	const LIST_KEY_VERSIONS_ENDPOINT: &'static str = "/listKeyVersions";
+
+	#[tokio::test]
+	async fn test_get() {
+		// Spin-up mock server with mock response for given request.
+		let base_url = mockito::server_url().to_string();
+
+		// Set up the mock request/response.
+		let get_request = GetObjectRequest { store_id: "store".to_string(), key: "k1".to_string() };
+		let mock_response = GetObjectResponse {
+			value: Some(KeyValue { key: "k1".to_string(), version: 2, value: b"k1v2".to_vec() }),
+			..Default::default()
+		};
+
+		// Register the mock endpoint with the mockito server.
+		let mock_server = mockito::mock("POST", GET_OBJECT_ENDPOINT)
+			.match_body(get_request.encode_to_vec())
+			.with_status(200)
+			.with_body(mock_response.encode_to_vec())
+			.create();
+
+		// Create a new VssClient with the mock server URL.
+		let client = VssClient::new(&base_url);
+
+		let actual_result = client.get_object(&get_request).await.unwrap();
+
+		let expected_result = &mock_response;
+		assert_eq!(actual_result, *expected_result);
+
+		// Verify server endpoint was called exactly once.
+		mock_server.expect(1).assert();
+	}
+
+	#[tokio::test]
+	async fn test_put() {
+		// Spin-up mock server with mock response for given request.
+		let base_url = mockito::server_url().to_string();
+
+		// Set up the mock request/response.
+		let request = PutObjectRequest {
+			store_id: "store".to_string(),
+			global_version: Some(4),
+			transaction_items: vec![KeyValue { key: "k1".to_string(), version: 2, value: b"k1v3".to_vec() }],
+		};
+		let mock_response = PutObjectResponse::default();
+
+		// Register the mock endpoint with the mockito server.
+		let mock_server = mockito::mock("POST", PUT_OBJECT_ENDPOINT)
+			.match_body(request.encode_to_vec())
+			.with_status(200)
+			.with_body(mock_response.encode_to_vec())
+			.create();
+
+		// Create a new VssClient with the mock server URL.
+		let vss_client = VssClient::new(&base_url);
+		let actual_result = vss_client.put_object(&request).await.unwrap();
+
+		let expected_result = &mock_response;
+		assert_eq!(actual_result, *expected_result);
+
+		// Verify server endpoint was called exactly once.
+		mock_server.expect(1).assert();
+	}
+
+	#[tokio::test]
+	async fn test_list_key_versions() {
+		// Spin-up mock server with mock response for given request.
+		let base_url = mockito::server_url().to_string();
+
+		// Set up the mock request/response.
+		let request = ListKeyVersionsRequest {
+			store_id: "store".to_string(),
+			page_size: Some(5),
+			page_token: None,
+			key_prefix: Some("k".into()),
+		};
+
+		let mock_response = ListKeyVersionsResponse {
+			key_versions: vec![
+				KeyValue { key: "k1".to_string(), version: 3, value: vec![] },
+				KeyValue { key: "k2".to_string(), version: 1, value: vec![] },
+			],
+			global_version: Some(4),
+			next_page_token: Some("k2".into()),
+		};
+
+		// Register the mock endpoint with the mockito server.
+		let mock_server = mockito::mock("POST", LIST_KEY_VERSIONS_ENDPOINT)
+			.match_body(request.encode_to_vec())
+			.with_status(200)
+			.with_body(mock_response.encode_to_vec())
+			.create();
+
+		// Create a new VssClient with the mock server URL.
+		let client = VssClient::new(&base_url);
+
+		let actual_result = client.list_key_versions(&request).await.unwrap();
+
+		let expected_result = &mock_response;
+		assert_eq!(actual_result, *expected_result);
+
+		// Verify server endpoint was called exactly once.
+		mock_server.expect(1).assert();
+	}
+
+	#[tokio::test]
+	async fn test_invalid_request_err_handling() {
+		let base_url = mockito::server_url();
+		let vss_client = VssClient::new(&base_url);
+
+		// Invalid Request Error
+		let error_response = ErrorResponse {
+			error_code: ErrorCode::InvalidRequestException.into(),
+			message: "InvalidRequestException".to_string(),
+		};
+		let mock_server = mockito::mock("POST", Matcher::Any)
+			.with_status(400)
+			.with_body(&error_response.encode_to_vec())
+			.create();
+
+		let get_result = vss_client
+			.get_object(&GetObjectRequest { store_id: "store".to_string(), key: "k1".to_string() })
+			.await;
+		assert!(matches!(get_result.unwrap_err(), VssError::InvalidRequestError { .. }));
+
+		let put_result = vss_client
+			.put_object(&PutObjectRequest {
+				store_id: "store".to_string(),
+				global_version: Some(4),
+				transaction_items: vec![KeyValue { key: "k1".to_string(), version: 2, value: b"k1v3".to_vec() }],
+			})
+			.await;
+		assert!(matches!(put_result.unwrap_err(), VssError::InvalidRequestError { .. }));
+
+		let list_result = vss_client
+			.list_key_versions(&ListKeyVersionsRequest {
+				store_id: "store".to_string(),
+				page_size: Some(5),
+				page_token: None,
+				key_prefix: Some("k".into()),
+			})
+			.await;
+		assert!(matches!(list_result.unwrap_err(), VssError::InvalidRequestError { .. }));
+
+		// Verify 3 requests hit the server
+		mock_server.expect(3).assert();
+	}
+
+	#[tokio::test]
+	async fn test_conflict_err_handling() {
+		let base_url = mockito::server_url();
+		let vss_client = VssClient::new(&base_url);
+
+		// Conflict Error
+		let error_response =
+			ErrorResponse { error_code: ErrorCode::ConflictException.into(), message: "ConflictException".to_string() };
+		let mock_server = mockito::mock("POST", Matcher::Any)
+			.with_status(409)
+			.with_body(&error_response.encode_to_vec())
+			.create();
+
+		let put_result = vss_client
+			.put_object(&PutObjectRequest {
+				store_id: "store".to_string(),
+				global_version: Some(4),
+				transaction_items: vec![KeyValue { key: "k1".to_string(), version: 2, value: b"k1v3".to_vec() }],
+			})
+			.await;
+		assert!(matches!(put_result.unwrap_err(), VssError::ConflictError { .. }));
+
+		// Verify 1 requests hit the server
+		mock_server.expect(1).assert();
+	}
+
+	#[tokio::test]
+	async fn test_internal_server_err_handling() {
+		let base_url = mockito::server_url();
+		let vss_client = VssClient::new(&base_url);
+
+		// Internal Server Error
+		let error_response = ErrorResponse {
+			error_code: ErrorCode::InternalServerException.into(),
+			message: "InternalServerException".to_string(),
+		};
+		let mock_server = mockito::mock("POST", Matcher::Any)
+			.with_status(500)
+			.with_body(&error_response.encode_to_vec())
+			.create();
+
+		let get_result = vss_client
+			.get_object(&GetObjectRequest { store_id: "store".to_string(), key: "k1".to_string() })
+			.await;
+		assert!(matches!(get_result.unwrap_err(), VssError::InternalServerError { .. }));
+
+		let put_result = vss_client
+			.put_object(&PutObjectRequest {
+				store_id: "store".to_string(),
+				global_version: Some(4),
+				transaction_items: vec![KeyValue { key: "k1".to_string(), version: 2, value: b"k1v3".to_vec() }],
+			})
+			.await;
+		assert!(matches!(put_result.unwrap_err(), VssError::InternalServerError { .. }));
+
+		let list_result = vss_client
+			.list_key_versions(&ListKeyVersionsRequest {
+				store_id: "store".to_string(),
+				page_size: Some(5),
+				page_token: None,
+				key_prefix: Some("k".into()),
+			})
+			.await;
+		assert!(matches!(list_result.unwrap_err(), VssError::InternalServerError { .. }));
+
+		// Verify 3 requests hit the server
+		mock_server.expect(3).assert();
+	}
+
+	#[tokio::test]
+	async fn test_internal_err_handling() {
+		let base_url = mockito::server_url();
+		let vss_client = VssClient::new(&base_url);
+
+		let error_response = ErrorResponse { error_code: 999, message: "UnknownException".to_string() };
+		let mut _mock_server = mockito::mock("POST", Matcher::Any)
+			.with_status(999)
+			.with_body(&error_response.encode_to_vec())
+			.create();
+
+		let get_request = GetObjectRequest { store_id: "store".to_string(), key: "k1".to_string() };
+		let get_result = vss_client.get_object(&get_request).await;
+		assert!(matches!(get_result.unwrap_err(), VssError::InternalError { .. }));
+
+		let put_request = PutObjectRequest {
+			store_id: "store".to_string(),
+			global_version: Some(4),
+			transaction_items: vec![KeyValue { key: "k1".to_string(), version: 2, value: b"k1v3".to_vec() }],
+		};
+		let put_result = vss_client.put_object(&put_request).await;
+		assert!(matches!(put_result.unwrap_err(), VssError::InternalError { .. }));
+
+		let list_request = ListKeyVersionsRequest {
+			store_id: "store".to_string(),
+			page_size: Some(5),
+			page_token: None,
+			key_prefix: Some("k".into()),
+		};
+		let list_result = vss_client.list_key_versions(&list_request).await;
+		assert!(matches!(list_result.unwrap_err(), VssError::InternalError { .. }));
+
+		let malformed_error_response = b"malformed";
+		_mock_server = mockito::mock("POST", Matcher::Any)
+			.with_status(409)
+			.with_body(&malformed_error_response)
+			.create();
+
+		let get_malformed_err_response = vss_client.get_object(&get_request).await;
+		assert!(matches!(get_malformed_err_response.unwrap_err(), VssError::InternalError { .. }));
+
+		let put_malformed_err_response = vss_client.put_object(&put_request).await;
+		assert!(matches!(put_malformed_err_response.unwrap_err(), VssError::InternalError { .. }));
+
+		let list_malformed_err_response = vss_client.list_key_versions(&list_request).await;
+		assert!(matches!(list_malformed_err_response.unwrap_err(), VssError::InternalError { .. }));
+
+		// Requests to endpoints are no longer mocked and will result in network error.
+		drop(_mock_server);
+
+		let get_network_err = vss_client.get_object(&get_request).await;
+		assert!(matches!(get_network_err.unwrap_err(), VssError::InternalError { .. }));
+
+		let put_network_err = vss_client.put_object(&put_request).await;
+		assert!(matches!(put_network_err.unwrap_err(), VssError::InternalError { .. }));
+
+		let list_network_err = vss_client.list_key_versions(&list_request).await;
+		assert!(matches!(list_network_err.unwrap_err(), VssError::InternalError { .. }));
+	}
+}