diff --git a/.gitignore b/.gitignore
index 63248c7..1c0d2cd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 node_modules/
 switchmon-*.tgz
 coverage
+.lvimrc
diff --git a/cli.js b/cli.js
index d71c69b..7dcddc3 100755
--- a/cli.js
+++ b/cli.js
@@ -16,20 +16,17 @@ function connectionStatus(device) {
 
 if (argv.help || argv.h) {
     console.log(usage);
-    process.exit(0);
-}
-
-const devices = swm.getDevices();
-
-if (argv.list || argv.l) {
-    devices
-        .then(devices => {
-            console.log('Detected devices:\n');
-            Object.keys(devices)
-                .sort(key => !devices[key].connected)
-                .forEach(key => console.log(key + ':', connectionStatus(devices[key])));
-            process.exit(0);
-        });
+    return;
+} else if (argv.list || argv.l) {
+    const devices = swm.getDevices((err, devices) => {
+        if (err) {
+            throw new Error(err);
+        }
+        console.log('Detected devices:\n');
+        Object.keys(devices)
+            .sort(key => !devices[key].connected)
+            .forEach(key => console.log(key + ':', connectionStatus(devices[key])));
+    });
 } else {
     let selectedMonitors = argv._;
 
@@ -42,14 +39,14 @@ if (argv.list || argv.l) {
         console.log('Using profile', profile);
     }
 
-    console.log('Switching on', selectedMonitors);
+    console.log('Switching on', selectedMonitors.length ? selectedMonitors : 'all connected monitors');
 
-    devices
-        .then(swm.generateXrandrOptions.bind(null, selectedMonitors))
-        .then(swm.switchDevices)
-        .then(swm.executePostCmd.bind(null, postCmd))
-        .catch(err => {
-            console.error(err);
-            process.exit(2);
-        });
+    swm.getDevices((err, devices) => {
+        if (err) {
+            throw new Error(err);
+        }
+        const xrandrOptions = swm.generateXrandrOptions(selectedMonitors, devices);
+        swm.switchDevices(xrandrOptions);
+        swm.executePostCmd(postCmd);
+    });
 }
diff --git a/swm.js b/swm.js
index 7a3bc1a..56940d4 100644
--- a/swm.js
+++ b/swm.js
@@ -3,28 +3,20 @@
 const xrandrParse = require('xrandr-parse');
 const exec = require('child_process').exec;
 
-function executeCmd(cmd) {
-    return new Promise((resolve, reject) => {
-        exec(cmd, (err, stdout, stderr) => {
-            if (err || stderr) {
-                reject(err);
-                return;
-            }
-            resolve(stdout);
-        });
-    });
+function executeCmd(cmd, callback) {
+    exec(cmd, callback);
 }
 
-function getDevices() {
-    return executeCmd('xrandr').then(stdout => xrandrParse(stdout));
+function getDevices(callback) {
+    executeCmd('xrandr', (err, stdout) => callback(err, err ? null : xrandrParse(stdout)));
 }
 
-function switchDevices(xrandrOptions) {
-    return executeCmd('xrandr ' + xrandrOptions);
+function switchDevices(xrandrOptions, callback) {
+    executeCmd('xrandr ' + xrandrOptions, callback);
 }
 
-function executePostCmd(postCmd) {
-    return executeCmd(postCmd);
+function executePostCmd(postCmd, callback) {
+    executeCmd(postCmd, callback);
 }
 
 function orderDeviceKeys(selectedDevices, devices) {
diff --git a/test/cli.tests.js b/test/cli.tests.js
new file mode 100644
index 0000000..e79b60f
--- /dev/null
+++ b/test/cli.tests.js
@@ -0,0 +1,116 @@
+'use strict';
+
+const sinon = require('sinon');
+const assert = require('assert');
+const proxyquire = require('proxyquire');
+
+describe('cli', () => {
+    let sandbox;
+    let consoleLogSpy;
+
+    beforeEach(() => {
+        sandbox = sinon.sandbox.create();
+        consoleLogSpy = sandbox.spy(console, 'log');
+    });
+
+    afterEach(function() {
+        sandbox.restore();
+    });
+
+    it('shows help', function() {
+        const minimistStub = sandbox.stub();
+        minimistStub.returns({h: true});
+
+        const cli = proxyquire('../cli.js', {
+            'minimist': minimistStub,
+            './usage.js': '[usage]'
+        });
+        assert.equal(consoleLogSpy.callCount, 1);
+        assert.equal(consoleLogSpy.args[0][0], '[usage]');
+    });
+
+    it('lists devices', function() {
+        const minimistStub = sandbox.stub();
+        minimistStub.returns({l: true});
+        const getDevicesStub = sandbox.stub();
+
+        proxyquire('../cli.js', {
+            'minimist': minimistStub,
+            './swm.js': {
+                getDevices: getDevicesStub
+            }
+        });
+        getDevicesStub.args[0][0](null, {
+            LVDS1: {connected: true},
+            HDMI2: {connected: false}
+        });
+
+        assert.equal(getDevicesStub.callCount, 1);
+        assert.equal(consoleLogSpy.callCount, 3);
+        assert.equal(consoleLogSpy.args[0][0], 'Detected devices:\n');
+        assert.equal(consoleLogSpy.args[1].join(' '), 'LVDS1: Connected');
+        assert.equal(consoleLogSpy.args[2].join(' '), 'HDMI2: Disconnected');
+    });
+
+    describe('switching', () => {
+        let minimistStub;
+        let selectedMonitors;
+        let deviceData;
+        let getDevicesStub;
+        let generateXrandrOptionsStub;
+        let switchDevicesStub;
+        let executePostCmdStub;
+
+        beforeEach(() => {
+            selectedMonitors = ['LVDS1'];
+            minimistStub = sandbox.stub();
+            minimistStub.returns({
+                _: selectedMonitors,
+                postCmd: '[some post cmd]'
+            });
+
+            deviceData = {
+                LVDS1: {connected: true},
+                HDMI2: {connected: false}
+            };
+
+            getDevicesStub = sandbox.stub();
+            generateXrandrOptionsStub = sandbox.stub().returns('[some xrandr options]');
+            switchDevicesStub = sandbox.stub();
+            executePostCmdStub = sandbox.stub();
+
+            const cli = proxyquire('../cli.js', {
+                'minimist': minimistStub,
+                './swm.js': {
+                    getDevices: getDevicesStub,
+                    generateXrandrOptions: generateXrandrOptionsStub,
+                    switchDevices: switchDevicesStub,
+                    executePostCmd: executePostCmdStub
+                },
+                './config.js': {}
+            });
+
+            getDevicesStub.args[0][0](null, deviceData);
+        });
+
+        it('calls getDevices', () => {
+            assert.equal(getDevicesStub.callCount, 1, 'calls device stub');
+        });
+
+        it('calls generateXrandrOptions', () => {
+            assert.equal(generateXrandrOptionsStub.callCount, 1, 'calls generateXrandrOptions');
+            assert.equal(generateXrandrOptionsStub.args[0][0], selectedMonitors);
+        });
+
+        it('calls switchDevices', () => {
+           assert.equal(switchDevicesStub.callCount, 1);
+           assert.equal(switchDevicesStub.args[0][0], '[some xrandr options]');
+        });
+
+        it('calls executePostCmd', () => {
+           assert.equal(executePostCmdStub.callCount, 1);
+           assert.equal(executePostCmdStub.args[0][0], '[some post cmd]');
+        });
+    });
+});
+
diff --git a/test/swm.tests.js b/test/swm.tests.js
index a3d4a34..2a212c4 100644
--- a/test/swm.tests.js
+++ b/test/swm.tests.js
@@ -32,43 +32,32 @@ describe('swm', () => {
         });
 
         it('calls exec', () => {
-            swm.getDevices();
+            swm.getDevices(sandbox.stub());
 
             assert.equal(execStub.callCount, 1);
             assert.equal(execStub.args[0][0], 'xrandr');
         });
 
-        it('returns promise', () => {
-            const devices = swm.getDevices();
-            assert.equal(typeof devices.then, 'function');
-            assert.equal(typeof devices.catch, 'function');
-        });
-
-        it('rejects when exec passes error', (done) => {
-            const devices = swm.getDevices();
-            const cb = execStub.args[0][1];
-            cb('some error');
-
-            return devices.catch((err) => {
+        it('passes error when exec passes error', (done) => {
+            const devices = swm.getDevices((err, devices) => {
                 assert.equal(xrandrParseStub.callCount, 0);
                 assert.equal(err, 'some error');
                 done();
             });
-
+            const cb = execStub.args[0][1];
+            cb('some error');
         });
 
         it('parses result', (done) => {
-            xrandrParseStub.returns('some result');
-            const devices = swm.getDevices();
-            const cb = execStub.args[0][1];
-            cb(null, 'stdout');
-
-            return devices.then((result) => {
-                assert.equal(xrandrParseStub.args[0][0], 'stdout');
+            xrandrParseStub.returns('[some result]');
+            swm.getDevices((err, devices) => {
+                assert.equal(xrandrParseStub.args[0][0], '[some stdout]');
                 assert.equal(xrandrParseStub.callCount, 1);
-                assert.equal(result, 'some result');
+                assert.equal(devices, '[some result]');
                 done();
             });
+            const cb = execStub.args[0][1];
+            cb(null, '[some stdout]');
         });
     });
 
@@ -144,27 +133,19 @@ describe('swm', () => {
         });
 
         it('calls exec with xrandr and opitons', () => {
-            swm.switchDevices('[some options]');
+            swm.switchDevices('[some options]', sandbox.stub());
 
             assert.equal(execStub.callCount, 1);
             assert.equal(execStub.args[0][0], 'xrandr [some options]');
         });
 
-        it('returns promise', () => {
-            const promise = swm.switchDevices('[some options]');
-            assert.equal(typeof promise.then, 'function');
-            assert.equal(typeof promise.catch, 'function');
-        });
-
-        it('rejects when exec passes error', (done) => {
-            const promise = swm.switchDevices('[some options]');
-            const cb = execStub.args[0][1];
-            cb('some error');
-
-            return promise.catch((err) => {
+        it('passes error when exec passes error', (done) => {
+            swm.switchDevices('[some options]', (err, devices) => {
                 assert.equal(err, 'some error');
                 done();
             });
+            const cb = execStub.args[0][1];
+            cb('some error');
         });
     });
 
@@ -188,21 +169,13 @@ describe('swm', () => {
             assert.equal(execStub.args[0][0], '[some cmd]');
         });
 
-        it('returns promise', () => {
-            const promise = swm.executePostCmd('[some cmd]');
-            assert.equal(typeof promise.then, 'function');
-            assert.equal(typeof promise.catch, 'function');
-        });
-
-        it('rejects when exec passes error', (done) => {
-            const promise = swm.executePostCmd('[some cmd]');
-            const cb = execStub.args[0][1];
-            cb('some error');
-
-            return promise.catch((err) => {
-                assert.equal(err, 'some error');
+        it('passes error when exec passes error', (done) => {
+            swm.executePostCmd('[some cmd]', (err, devices) => {
+                assert.equal(err, '[some error]');
                 done();
             });
+            const cb = execStub.args[0][1];
+            cb('[some error]');
         });
     });
 });