diff --git a/pom.xml b/pom.xml
index 166bc7e..bad763c 100644
--- a/pom.xml
+++ b/pom.xml
@@ -31,6 +31,13 @@
             <artifactId>jnativehook</artifactId>
             <version>2.2.2</version>
         </dependency>
+
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>6.1.3</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <distributionManagement>
@@ -48,6 +55,12 @@
 
     <build>
         <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>3.6.0</version>
+            </plugin>
+
             <plugin>
                 <groupId>org.sonarsource.scanner.maven</groupId>
                 <artifactId>sonar-maven-plugin</artifactId>
diff --git a/src/main/java/wtf/beatrice/autosqueal/util/SystemUtil.java b/src/main/java/wtf/beatrice/autosqueal/util/SystemUtil.java
index 4df5939..3fe43d0 100644
--- a/src/main/java/wtf/beatrice/autosqueal/util/SystemUtil.java
+++ b/src/main/java/wtf/beatrice/autosqueal/util/SystemUtil.java
@@ -6,14 +6,18 @@ public class SystemUtil
 {
 
     public static OperatingSystem getHostSystem() {
-        String osName = System.getProperty("os.name").toLowerCase(Locale.ENGLISH);
-        if (osName.contains("win")) {
+        return fromOsName(System.getProperty("os.name"));
+    }
+
+    public static OperatingSystem fromOsName(String osName) {
+        String normalizedOsName = osName.toLowerCase(Locale.ENGLISH);
+        if (normalizedOsName.contains("win")) {
             return OperatingSystem.WINDOWS;
-        } else if (osName.contains("nix") ||
-                osName.contains("nux") ||
-                osName.contains("aix")) {
+        } else if (normalizedOsName.contains("nix") ||
+                normalizedOsName.contains("nux") ||
+                normalizedOsName.contains("aix")) {
             return OperatingSystem.LINUX;
-        } else if (osName.contains("mac")) {
+        } else if (normalizedOsName.contains("mac")) {
             return OperatingSystem.MAC_OS;
         } else {
             return OperatingSystem.UNKNOWN;
diff --git a/src/test/java/wtf/beatrice/autosqueal/controls/SingleStepMovementTaskTest.java b/src/test/java/wtf/beatrice/autosqueal/controls/SingleStepMovementTaskTest.java
new file mode 100644
index 0000000..bf1cb42
--- /dev/null
+++ b/src/test/java/wtf/beatrice/autosqueal/controls/SingleStepMovementTaskTest.java
@@ -0,0 +1,117 @@
+package wtf.beatrice.autosqueal.controls;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.fail;
+
+class SingleStepMovementTaskTest
+{
+    private static final int MAX_TICKS = 20_000;
+    private static final float DELTA = 0.0f;
+
+    @Test
+    void noStepWhenAlreadyAtDestination() {
+        assertEquals(0.0f, SingleStepMovementTask.computeStepX(0, 0), DELTA);
+        assertEquals(0.0f, SingleStepMovementTask.computeStepY(0, 0), DELTA);
+    }
+
+    @Test
+    void axisAlignedMovementsProduceNoInfiniteSteps() {
+        // moving only horizontally: the y step must be 0, not Infinity or NaN
+        assertEquals(1.0f, SingleStepMovementTask.computeStepX(100, 0), DELTA);
+        assertEquals(0.0f, SingleStepMovementTask.computeStepY(100, 0), DELTA);
+
+        // moving only vertically: the x step must be 0, not Infinity or NaN
+        assertEquals(0.0f, SingleStepMovementTask.computeStepX(0, 100), DELTA);
+        assertEquals(1.0f, SingleStepMovementTask.computeStepY(0, 100), DELTA);
+    }
+
+    @Test
+    void diagonalMovementsMoveBothAxes() {
+        assertEquals(1.0f, SingleStepMovementTask.computeStepX(100, 100), DELTA);
+        assertEquals(1.0f, SingleStepMovementTask.computeStepY(100, 100), DELTA);
+
+        assertEquals(0.5f, SingleStepMovementTask.computeStepX(50, 100), DELTA);
+        assertEquals(1.0f, SingleStepMovementTask.computeStepY(50, 100), DELTA);
+
+        assertEquals(1.0f, SingleStepMovementTask.computeStepX(100, 50), DELTA);
+        assertEquals(0.5f, SingleStepMovementTask.computeStepY(100, 50), DELTA);
+    }
+
+    @Test
+    void stepsAreNeverInfiniteOrNaN() {
+        for (int lengthX = 0; lengthX <= 400; lengthX += 7) {
+            for (int lengthY = 0; lengthY <= 400; lengthY += 7) {
+                float stepX = SingleStepMovementTask.computeStepX(lengthX, lengthY);
+                float stepY = SingleStepMovementTask.computeStepY(lengthX, lengthY);
+
+                assertFalse(Float.isInfinite(stepX), "infinite stepX for lengths [" + lengthX + ", " + lengthY + "]");
+                assertFalse(Float.isNaN(stepX), "NaN stepX for lengths [" + lengthX + ", " + lengthY + "]");
+                assertFalse(Float.isInfinite(stepY), "infinite stepY for lengths [" + lengthX + ", " + lengthY + "]");
+                assertFalse(Float.isNaN(stepY), "NaN stepY for lengths [" + lengthX + ", " + lengthY + "]");
+            }
+        }
+    }
+
+    @Test
+    void advanceMovesTowardTheDestination() {
+        assertEquals(5.0f, SingleStepMovementTask.advance(5.0f, 5.0f, 1.0f), DELTA); // already there
+        assertEquals(9.0f, SingleStepMovementTask.advance(10.0f, 5.0f, 1.0f), DELTA); // decreasing
+        assertEquals(6.0f, SingleStepMovementTask.advance(5.0f, 10.0f, 1.0f), DELTA); // increasing
+    }
+
+    @Test
+    void adjustedStepUsesExactRemainderWhenClose() {
+        assertEquals(0.4f, SingleStepMovementTask.adjustedStep(10.0f, 10.4f, 1.0f), 0.00001f);
+        assertEquals(0.4f, SingleStepMovementTask.adjustedStep(10.8f, 10.4f, 1.0f), 0.00001f);
+        assertEquals(1.0f, SingleStepMovementTask.adjustedStep(10.0f, 20.0f, 1.0f), DELTA);
+    }
+
+    @Test
+    void movementConvergesToDestination() {
+        record MovementCase(float startX, float startY, int destX, int destY) {}
+
+        MovementCase[] cases = {
+                new MovementCase(100, 100, 500, 500),   // plain diagonal
+                new MovementCase(500, 500, 100, 100),   // going up-left
+                new MovementCase(100, 100, 500, 100),   // horizontal (used to break: infinite step)
+                new MovementCase(500, 100, 100, 100),   // horizontal, other direction
+                new MovementCase(100, 100, 100, 500),   // vertical (used to break: infinite step)
+                new MovementCase(100, 500, 100, 100),   // vertical, other direction
+                new MovementCase(105, 105, 105, 105),   // already at destination
+                new MovementCase(0, 0, 2000, 1000),     // steep diagonal
+                new MovementCase(2000, 1000, 0, 0),     // same, backwards
+                new MovementCase(37, 173, 2311, 997),   // random-ish, both directions mixed
+        };
+
+        for (MovementCase move : cases) {
+            float x = move.startX();
+            float y = move.startY();
+
+            int lengthX = Math.round(Math.abs(x - move.destX()));
+            int lengthY = Math.round(Math.abs(y - move.destY()));
+            float stepX = SingleStepMovementTask.computeStepX(lengthX, lengthY);
+            float stepY = SingleStepMovementTask.computeStepY(lengthX, lengthY);
+
+            boolean converged = false;
+            for (int tick = 0; tick < MAX_TICKS; tick++) {
+                if (Math.round(x) == move.destX() && Math.round(y) == move.destY()) {
+                    converged = true;
+                    break;
+                }
+
+                stepX = SingleStepMovementTask.adjustedStep(x, move.destX(), stepX);
+                stepY = SingleStepMovementTask.adjustedStep(y, move.destY(), stepY);
+                x = SingleStepMovementTask.advance(x, move.destX(), stepX);
+                y = SingleStepMovementTask.advance(y, move.destY(), stepY);
+            }
+
+            if (!converged) {
+                fail("movement did not converge: stuck at [" + Math.round(x) + ", " + Math.round(y)
+                        + "] while heading to [" + move.destX() + ", " + move.destY() + "]");
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/wtf/beatrice/autosqueal/util/SystemUtilTest.java b/src/test/java/wtf/beatrice/autosqueal/util/SystemUtilTest.java
new file mode 100644
index 0000000..f2f1427
--- /dev/null
+++ b/src/test/java/wtf/beatrice/autosqueal/util/SystemUtilTest.java
@@ -0,0 +1,34 @@
+package wtf.beatrice.autosqueal.util;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class SystemUtilTest
+{
+    @Test
+    void detectsWindows() {
+        assertEquals(SystemUtil.OperatingSystem.WINDOWS, SystemUtil.fromOsName("Windows 11"));
+    }
+
+    @Test
+    void detectsLinux() {
+        assertEquals(SystemUtil.OperatingSystem.LINUX, SystemUtil.fromOsName("Linux"));
+        assertEquals(SystemUtil.OperatingSystem.LINUX, SystemUtil.fromOsName("GNU/Linux"));
+    }
+
+    @Test
+    void detectsMacOS() {
+        assertEquals(SystemUtil.OperatingSystem.MAC_OS, SystemUtil.fromOsName("Mac OS X"));
+    }
+
+    @Test
+    void unknownForOtherSystems() {
+        assertEquals(SystemUtil.OperatingSystem.UNKNOWN, SystemUtil.fromOsName("SunOS"));
+    }
+
+    @Test
+    void hostSystemMatchesOsName() {
+        assertEquals(SystemUtil.fromOsName(System.getProperty("os.name")), SystemUtil.getHostSystem());
+    }
+}
\ No newline at end of file