diff --git a/src/cmd/cloud.js b/src/cmd/cloud.js
index a5571c9ec..b33703052 100644
--- a/src/cmd/cloud.js
+++ b/src/cmd/cloud.js
@@ -1,8 +1,6 @@
 const _ = require('lodash');
 const VError = require('verror');
-const whenNode = require('when/node');
 const prompt = require('inquirer').prompt;
-const temp = require('temp').track();
 
 const settings = require('../../settings.js');
 const specs = require('../lib/deviceSpecs');
diff --git a/src/cmd/function.js b/src/cmd/function.js
index 4c9834ecc..1d956d2fb 100644
--- a/src/cmd/function.js
+++ b/src/cmd/function.js
@@ -3,10 +3,6 @@ const VError = require('verror');
 const ensureError = require('../lib/utilities').ensureError;
 
 class FunctionCommand {
-	constructor(options) {
-		this.options = options;
-	}
-
 	listFunctions() {
 		const api = new ApiClient();
 		api.ensureToken();
@@ -42,7 +38,7 @@ class FunctionCommand {
 		api.ensureToken();
 
 		return api.callFunction(deviceId, functionName, funcParam).then(result => {
-			if (result && result.return_value) {
+			if (result && result.hasOwnProperty('return_value')) {
 				console.log(result.return_value);
 			} else {
 				throw api.normalizedApiError(result);
diff --git a/src/cmd/variable.js b/src/cmd/variable.js
index 7a168d9c7..d5b87b9af 100644
--- a/src/cmd/variable.js
+++ b/src/cmd/variable.js
@@ -67,7 +67,7 @@ class VariableCommand {
 		return when.map(deviceId, (deviceId) => {
 			return api.getVariable(deviceId, variableName);
 		}).then((results) => {
-			const time = moment().format();
+			const now = moment().format();
 			let hasErrors = false;
 			for (let i = 0; i < results.length; i++) {
 				const parts = [];
@@ -82,7 +82,7 @@ class VariableCommand {
 					parts.push(result.coreInfo.deviceID);
 				}
 				if (time) {
-					parts.push(time);
+					parts.push(now);
 				}
 				parts.push(result.result);
 
diff --git a/test/cmd/function.spec.js b/test/cmd/function.spec.js
new file mode 100644
index 000000000..0330a395e
--- /dev/null
+++ b/test/cmd/function.spec.js
@@ -0,0 +1,109 @@
+const expect = require('chai').expect;
+const proxyquire = require('proxyquire');
+const sandbox = require('sinon').createSandbox();
+
+const stubs = {
+	api: {
+		ensureToken: () => {},
+		callFunction: () => {},
+		normalizedApiError: (resp) => new Error(resp.error),
+	},
+	ApiClient: function ApiClient(){
+		return stubs.api;
+	}
+};
+
+const FunctionCommand = proxyquire('../../src/cmd/function', {
+	'../lib/ApiClient.js': stubs.ApiClient
+});
+
+
+describe('Function Command', () => {
+
+	let deviceId, functionName, functionParam;
+
+	beforeEach(() => {
+		deviceId = 'test-device';
+		functionName = 'fn';
+		functionParam = 'param';
+	});
+
+	afterEach(() => {
+		sandbox.restore();
+	});
+
+	describe('when the function succeeds', () => {
+		it('prints the return value', withConsoleStubs(() => {
+			const { func, api } = stubForFunction(new FunctionCommand(), stubs);
+			api.callFunction.resolves({ ok: true, return_value: 42 });
+
+			return func.callFunction(deviceId, functionName, functionParam).then(() => {
+				expectSuccessMessage(42);
+			});
+		}));
+
+		it('prints the return value of 0', withConsoleStubs(() => {
+			const { func, api } = stubForFunction(new FunctionCommand(), stubs);
+			api.callFunction.resolves({ ok: true, return_value: 0 });
+
+			return func.callFunction(deviceId, functionName, functionParam).then(() => {
+				expectSuccessMessage(0);
+			});
+		}));
+	});
+
+	describe('when the function does not exist', () => {
+		it('rejects with an error',() => {
+			const { func, api } = stubForFunction(new FunctionCommand(), stubs);
+			api.callFunction.resolves({
+				ok: false,
+				error: `Function ${functionName} not found`
+			});
+
+			return func.callFunction(deviceId, functionName, functionParam).then(() => {
+				throw new Error('expected promise to be rejected');
+			}).catch(error => {
+				expect(error).to.have.property('message', `Function call failed: Function ${functionName} not found`);
+			});
+		});
+	});
+
+	function expectSuccessMessage(value){
+		expect(process.stdout.write).to.have.property('callCount', 1);
+		expect(process.stdout.write.firstCall.args[0])
+			.to.match(new RegExp(`${value}\\n$`));
+	}
+
+	function stubForFunction(func, stubs){
+		const { api } = stubs;
+		sandbox.stub(api, 'ensureToken');
+		sandbox.stub(api, 'callFunction');
+		return { func, api };
+	}
+
+	// TODO (mirande): figure out a better approach. this allows us to verify
+	// log output without supressing mocha's success / error messages but is a
+	// bit awkward
+	function withConsoleStubs(fn){
+
+		return () => {
+			let result;
+
+			sandbox.stub(process.stdout, 'write');
+			sandbox.stub(process.stderr, 'write');
+
+			try {
+				result = fn();
+			} catch (error) {
+				sandbox.restore();
+				throw error;
+			}
+
+			if (result && typeof result.finally === 'function'){
+				return result.finally(() => sandbox.restore());
+			}
+			sandbox.restore();
+			return result;
+		};
+	}
+});