diff --git a/.gitignore b/.gitignore
index 00c301e..04561b3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,9 @@
 /problems
+tmp
+
+# Ignore these to avoid leaking local replacements to the devkit
+./go.mod
+./go.sum
+
+go.mod
+go.sum
\ No newline at end of file
diff --git a/tests/tests.go b/tests/tests.go
new file mode 100644
index 0000000..b30ef32
--- /dev/null
+++ b/tests/tests.go
@@ -0,0 +1,56 @@
+package tests
+
+import (
+	"fmt"
+	"os"
+	"testing"
+	"time"
+
+	"git.bizdoc.ro/gabi-public/Advent-of-Code.git/aoc"
+)
+
+func assert(t *testing.T, err error, a, b any) {
+	t.Helper()
+
+	if err != nil {
+		t.Error(err)
+	}
+	want := fmt.Sprintf("%v", a)
+	got := fmt.Sprintf("%v", b)
+	if got != want {
+		err = fmt.Errorf("want %s, got %s", want, got)
+		t.Error(err)
+	}
+}
+
+func Handler[T any](f func(ctx aoc.Context) (T, error)) func(ctx aoc.Context) (any, error) {
+	return func(c aoc.Context) (any, error) {
+		return f(c)
+	}
+}
+
+func Handler2[T any, K any](param T, f func(ctx aoc.Context, param T) (K, error)) func(ctx aoc.Context) (any, error) {
+	return func(c aoc.Context) (any, error) {
+		return f(c, param)
+	}
+}
+
+func Test(t *testing.T, file string, handler func(aoc.Context) (any, error), want any) {
+	t.Helper()
+
+	f, err := os.Open("tmp/" + file)
+	if err != nil {
+		panic(err)
+	}
+	defer f.Close()
+
+	start := time.Now()
+	got, err := handler(aoc.Context{
+		Body:    f,
+		Logger:  nil,
+		Context: nil,
+	})
+	t.Log("took", time.Since(start))
+
+	assert(t, err, want, got)
+}