diff --git a/src/se/vidstige/jadb/AdbServerLauncher.java b/src/se/vidstige/jadb/AdbServerLauncher.java
index 762197f..28bc271 100644
--- a/src/se/vidstige/jadb/AdbServerLauncher.java
+++ b/src/se/vidstige/jadb/AdbServerLauncher.java
@@ -1,32 +1,30 @@
 package se.vidstige.jadb;
 
 import java.io.IOException;
+import java.util.Map;
 
 /**
  * Launches the ADB server
  */
 public class AdbServerLauncher {
-    private Runtime runtime;
+    private final String executable;
+    private Subprocess subprocess;
 
-    public AdbServerLauncher() {
-        this(Runtime.getRuntime());
+    public AdbServerLauncher(Subprocess subprocess, Map<String, String> environment) {
+        this.subprocess = subprocess;
+        this.executable = findAdbExecutable(environment);
     }
 
-    public AdbServerLauncher(Runtime runtime) {
-        this.runtime = runtime;
-    }
-
-    private String findAdbExecutable() {
-        String android_home = System.getenv("ANDROID_HOME");
+    private static String findAdbExecutable(Map<String, String> environment) {
+        String android_home = environment.get("ANDROID_HOME");
         if (android_home == null || android_home.equals("")) {
             return "adb";
         }
-
         return android_home + "/platform-tools/adb";
     }
 
     public void launch() throws IOException, InterruptedException {
-        Process p = runtime.exec(new String[]{findAdbExecutable(), "start-server"});
+        Process p = subprocess.execute(new String[]{executable, "start-server"});
         p.waitFor();
         int exitValue = p.exitValue();
         if (exitValue != 0) throw new IOException("adb exited with exit code: " + exitValue);
diff --git a/src/se/vidstige/jadb/Subprocess.java b/src/se/vidstige/jadb/Subprocess.java
new file mode 100644
index 0000000..082d98c
--- /dev/null
+++ b/src/se/vidstige/jadb/Subprocess.java
@@ -0,0 +1,9 @@
+package se.vidstige.jadb;
+
+import java.io.IOException;
+
+public class Subprocess {
+    public Process execute(String[] command) throws IOException {
+        return Runtime.getRuntime().exec(command);
+    }
+}
diff --git a/test/se/vidstige/jadb/test/fakes/FakeProcess.java b/test/se/vidstige/jadb/test/fakes/FakeProcess.java
new file mode 100644
index 0000000..7ea2c1d
--- /dev/null
+++ b/test/se/vidstige/jadb/test/fakes/FakeProcess.java
@@ -0,0 +1,41 @@
+package se.vidstige.jadb.test.fakes;
+
+import java.io.InputStream;
+import java.io.OutputStream;
+
+public class FakeProcess extends Process {
+    private final int exitValue;
+
+    public FakeProcess(int exitValue) {
+        this.exitValue = exitValue;
+    }
+
+    @Override
+    public OutputStream getOutputStream() {
+        return null;
+    }
+
+    @Override
+    public InputStream getInputStream() {
+        return null;
+    }
+
+    @Override
+    public InputStream getErrorStream() {
+        return null;
+    }
+
+    @Override
+    public int waitFor() throws InterruptedException {
+        return 0;
+    }
+
+    @Override
+    public int exitValue() {
+        return exitValue;
+    }
+
+    @Override
+    public void destroy() {
+    }
+}
diff --git a/test/se/vidstige/jadb/test/fakes/FakeSubprocess.java b/test/se/vidstige/jadb/test/fakes/FakeSubprocess.java
new file mode 100644
index 0000000..a09556b
--- /dev/null
+++ b/test/se/vidstige/jadb/test/fakes/FakeSubprocess.java
@@ -0,0 +1,72 @@
+package se.vidstige.jadb.test.fakes;
+
+import se.vidstige.jadb.Subprocess;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class FakeSubprocess extends Subprocess {
+    private List<Expectation> expectations = new ArrayList<>();
+
+    public Expectation expect(String[] command, int exitValue) {
+        Expectation builder = new Expectation(command, exitValue);
+        expectations.add(builder);
+        return builder;
+    }
+
+    private String format(String[] command) {
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < command.length; i++) {
+            if (i > 0) {
+                sb.append(" ");
+            }
+            sb.append(command[i]);
+        }
+        return sb.toString();
+    }
+
+    @Override
+    public Process execute(String[] command) throws IOException {
+        List<Expectation> toRemove = new ArrayList<>();
+        for (Expectation e : expectations) {
+            if (e.matches(command)) {
+                toRemove.add(e);
+            }
+        }
+        expectations.removeAll(toRemove);
+        if (toRemove.size() == 1) {
+            return new FakeProcess(toRemove.get(0).getExitValue());
+        }
+        throw new AssertionError("Unexpected command: " + format(command));
+    }
+
+    public void verifyExpectations() {
+        if (expectations.size() > 0) {
+            throw new AssertionError("Subprocess never called: " + format(expectations.get(0).getCommand()));
+        }
+    }
+
+    private class Expectation {
+        private final String[] command;
+        private final int exitValue;
+
+        public Expectation(String[] command, int exitValue) {
+            this.command = command;
+            this.exitValue = exitValue;
+        }
+
+        public boolean matches(String[] command) {
+            return Arrays.equals(command, this.command);
+        }
+
+        public int getExitValue() {
+            return exitValue;
+        }
+
+        public String[] getCommand() {
+            return command;
+        }
+    }
+}
diff --git a/test/se/vidstige/jadb/test/integration/RealDeviceTestCases.java b/test/se/vidstige/jadb/test/integration/RealDeviceTestCases.java
index aaa222e..134353f 100644
--- a/test/se/vidstige/jadb/test/integration/RealDeviceTestCases.java
+++ b/test/se/vidstige/jadb/test/integration/RealDeviceTestCases.java
@@ -23,7 +23,7 @@ public class RealDeviceTestCases {
     @BeforeClass
     public static void tryToStartAdbServer() {
         try {
-            new AdbServerLauncher().launch();
+            new AdbServerLauncher(new Subprocess(), System.getenv()).launch();
         } catch (IOException e) {
             System.out.println("Could not start adb-server");
         } catch (InterruptedException e) {
diff --git a/test/se/vidstige/jadb/test/unit/AdbServerLauncherFixture.java b/test/se/vidstige/jadb/test/unit/AdbServerLauncherFixture.java
new file mode 100644
index 0000000..a9b5192
--- /dev/null
+++ b/test/se/vidstige/jadb/test/unit/AdbServerLauncherFixture.java
@@ -0,0 +1,45 @@
+package se.vidstige.jadb.test.unit;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import se.vidstige.jadb.AdbServerLauncher;
+import se.vidstige.jadb.test.fakes.FakeSubprocess;
+
+import java.io.IOException;
+import java.util.*;
+
+public class AdbServerLauncherFixture {
+
+    private FakeSubprocess subprocess;
+    private Map<String, String> environment = new HashMap<>();
+
+    @Before
+    public void setUp() {
+        subprocess = new FakeSubprocess();
+    }
+    @After
+    public void tearDown() {
+        subprocess.verifyExpectations();
+    }
+
+    @Test
+    public void testStartServer() throws Exception {
+        subprocess.expect(new String[]{"/abc/platform-tools/adb", "start-server"}, 0);
+        Map<String, String> environment = new HashMap<>();
+        environment.put("ANDROID_HOME", "/abc");
+        new AdbServerLauncher(subprocess, environment).launch();
+    }
+
+    @Test
+    public void testStartServerWithoutANDROID_HOME() throws Exception {
+        subprocess.expect(new String[]{"adb", "start-server"}, 0);
+        new AdbServerLauncher(subprocess, environment).launch();
+    }
+
+    @Test(expected=IOException.class)
+    public void testStartServerFails() throws Exception {
+        subprocess.expect(new String[]{"adb", "start-server"}, -1);
+        new AdbServerLauncher(subprocess, environment).launch();
+    }
+}