diff --git a/swm.js b/swm.js
index 026b60b..56940d4 100644
--- a/swm.js
+++ b/swm.js
@@ -8,7 +8,7 @@ function executeCmd(cmd, callback) {
 }
 
 function getDevices(callback) {
-    executeCmd('xrandr', (err, stdout) => callback(err, xrandrParse(stdout)));
+    executeCmd('xrandr', (err, stdout) => callback(err, err ? null : xrandrParse(stdout)));
 }
 
 function switchDevices(xrandrOptions, callback) {
diff --git a/test/cli.tests.js b/test/cli.tests.js
index d48addd..e79b60f 100644
--- a/test/cli.tests.js
+++ b/test/cli.tests.js
@@ -33,19 +33,18 @@ describe('cli', () => {
         const minimistStub = sandbox.stub();
         minimistStub.returns({l: true});
         const getDevicesStub = sandbox.stub();
-        getDevicesStub.returns({
-            then: cb => cb({
-                LVDS1: {connected: true},
-                HDMI2: {connected: false}
-            })
-        });
 
-        const cli = proxyquire('../cli.js', {
+        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');
@@ -75,9 +74,7 @@ describe('cli', () => {
                 HDMI2: {connected: false}
             };
 
-            getDevicesStub = sandbox.stub().returns({
-                then: cb => cb(deviceData)
-            });
+            getDevicesStub = sandbox.stub();
             generateXrandrOptionsStub = sandbox.stub().returns('[some xrandr options]');
             switchDevicesStub = sandbox.stub();
             executePostCmdStub = sandbox.stub();
@@ -92,6 +89,8 @@ describe('cli', () => {
                 },
                 './config.js': {}
             });
+
+            getDevicesStub.args[0][0](null, deviceData);
         });
 
         it('calls getDevices', () => {
@@ -111,7 +110,6 @@ describe('cli', () => {
         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]');
         });
     });
 });