diff --git a/fx92/drawing.py b/fx92/drawing.py
index 55ef608..e2d79a2 100644
--- a/fx92/drawing.py
+++ b/fx92/drawing.py
@@ -33,6 +33,8 @@ class Window:
 
         # Create the window
         mode = SDL_WINDOW_HIDDEN if self.quiet else SDL_WINDOW_SHOWN
+        # TODO: If the window is hidden, nothing is rendered
+        mode = SDL_WINDOW_SHOWN
         self.w = SDL_CreateWindow("fx-92 Scientifique Collège+".encode(),
             SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
             self.width*self.scale, self.height*self.scale, mode)
diff --git a/tests.py b/tests.py
new file mode 100755
index 0000000..c5ce8aa
--- /dev/null
+++ b/tests.py
@@ -0,0 +1,72 @@
+#! /usr/bin/python3
+
+import sys
+import glob
+import os.path
+import subprocess
+
+from PIL import Image
+from PIL import ImageChops
+
+def imgequal(ref, out):
+    ref = Image.open(ref)
+    out = Image.open(out)
+
+    diff = ImageChops.difference(ref, out)
+    return diff.getbbox() is None
+
+def runtest(program, refout=None, refimg=None):
+    st = subprocess.run("./fx92.py --quiet --save=/tmp/fx92-test.bmp".split()
+        + [program], stdout=subprocess.PIPE)
+
+    if st.returncode != 0:
+        print("  -> Execution FAILED!")
+        return 0
+
+    print("  Execution completed.")
+    success = True
+
+    if refout is not None:
+        with open(refout, "r") as fp:
+            refout = fp.read()
+        if st.stdout == refout:
+            print("  Output is correct.")
+        else:
+            print("  -> Output is incorrect!")
+            success = False
+
+    if refimg is not None:
+        if imgequal(refimg, "/tmp/fx92-test.bmp"):
+            print("  Image is correct.")
+        else:
+            print("  -> Image is incorrect!")
+            success = False
+
+    return success
+
+def main():
+    paths = glob.glob("tests/*.txt")
+    print("Found {} tests.".format(len(paths)))
+
+    total = 0
+    passed = 0
+
+    for t in paths:
+        print("\n{}:".format(t))
+
+        refout = t[:-4] + ".out"
+        refout = refout if os.path.isfile(refout) else None
+
+        refimg = t[:-4] + ".png"
+        refimg = refimg if os.path.isfile(refimg) else None
+
+        passed += runtest(t, refout=refout, refimg=refimg)
+        total += 1
+
+    if passed < total:
+        print("\nWarning, some tests failed!")
+        return 1
+    return 0
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/tests/corners.png b/tests/corners.png
new file mode 100644
index 0000000..8fd17ce
Binary files /dev/null and b/tests/corners.png differ
diff --git a/tests/corners.txt b/tests/corners.txt
new file mode 100644
index 0000000..ddbbc7c
--- /dev/null
+++ b/tests/corners.txt
@@ -0,0 +1,4 @@
+goto -90, 23; pendown; goto x-5, y; goto x, y-5; penup
+goto -90, -23; pendown; goto x-5, y; goto x, y+5; penup
+goto 91, 23; pendown; goto x+5, y; goto x, y-5; penup
+goto 91, -23; pendown; goto x+5, y; goto x, y+5; penup