diff --git a/.github/workflows/build+test.yml b/.github/workflows/build+test.yml
new file mode 100644
index 0000000..4b23954
--- /dev/null
+++ b/.github/workflows/build+test.yml
@@ -0,0 +1,22 @@
+name: Build/Test
+
+on: 
+  push:
+    branches:
+      - main
+    tags:
+      - 'v*.*.*'
+
+jobs:
+  test:
+    name: Test mothd
+    runs-on: ubuntu-latest
+    steps:
+      - name: Retrieve code
+        uses: actions/checkout@v2
+
+      - name: Build
+        run: make
+
+      - name: Test
+        run: ./test.sh
diff --git a/test.sh b/test.sh
new file mode 100755
index 0000000..a7cb8e6
--- /dev/null
+++ b/test.sh
@@ -0,0 +1,87 @@
+#! /bin/sh
+
+tests=0
+successes=0
+failures=0
+
+H () {
+    section="$*"
+    printf "\n%-20s " "$*"
+}
+
+title() {
+    thistest="$1"
+    tests=$(expr $tests + 1)
+}
+
+successes=0
+pass () {
+    printf '.'
+    successes=$(expr $successes + 1)
+}
+
+failures=0
+fail () {
+    printf '(%s)' "$thistest"
+    failures=$(expr $failures + 1)
+}
+
+
+H "xor"
+
+title "single-byte decimal"
+printf 'hello' | ./xor 22 | grep -q '~szzy' && pass || fail
+
+title "single-byte hex"
+printf 'hello' | ./xor 0x16 | grep -q '~szzy' && pass || fail
+
+title "single-byte -x"
+printf 'hello' | ./xor -x 16 | grep -q '~szzy' && pass || fail
+
+
+H "hex/unhex"
+
+title "hex"
+printf ' hello' | ./hex | grep -q '68 65 6c 6c 6f' && pass || fail
+
+title "unhex"
+echo '68 65 6c 6c 6f' | ./unhex | grep -q 'hello' && pass || fail
+
+
+H "slice"
+
+title "slice begin"
+printf 'hello' | ./slice 2 | grep -qx 'llo' && pass || fail
+
+title "slice begin + end"
+printf 'hello' | ./slice 2 4 | grep -qx 'll' && pass || fail
+
+title "slice begin + end + begin"
+printf 'hello' | ./slice 0 2 4 | grep -qx 'heo' && pass || fail
+
+
+H "hd"
+
+title "hd short"
+printf 'hello' | ./hd | grep -qx '00000000  68 65 6c 6c 6f.*hello' && pass || fail
+
+
+H "Everything else"
+
+title "entropy"
+printf 'hello' | ./entropy | grep -q 1.921928 && pass || fail
+
+title "pyesc"
+printf '\0hello\n' | ./pyesc | grep -xq '.x00hello.n' && pass || fail
+
+title "freq"
+printf 'hello' | ./freq | grep -xq '2 6c l' && pass || fail
+
+title "histogram"
+printf 'hello' | ./freq | ./histogram | grep -xq '6c l ## 2' && pass || fail
+
+echo
+echo
+echo "$successes of $tests tests passed ($failures failed)."
+
+exit $failures
\ No newline at end of file
diff --git a/xor.c b/xor.c
index 1bb135f..1253776 100644
--- a/xor.c
+++ b/xor.c
@@ -14,7 +14,7 @@ int main(int argc, char* argv[]) {
   int arg;
   int c;
 
-  while ((c = getopt(argc, argv, "ax")) != -1) {
+  while ((c = getopt(argc, argv, "x")) != -1) {
     switch (c) {
       case 'x':
         radix = 16;