diff --git a/.gitignore b/.gitignore
index b30a728..1fa929a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 *.o
 bin
+*.d.out
diff --git a/makefile b/makefile
index e7f53a6..4650bd7 100644
--- a/makefile
+++ b/makefile
@@ -6,3 +6,5 @@ FLAGS := -g -w $(INCLUDE_PATHS)
 all: $(SRC)
 	$(COMPILER) $(FLAGS) $(SRC) -ofbin/dfmt
 
+test: bin/dfmt
+	cd tests && ./test.sh
diff --git a/tests/frontpage.d b/tests/frontpage.d
new file mode 100644
index 0000000..e0062a6
--- /dev/null
+++ b/tests/frontpage.d
@@ -0,0 +1,15 @@
+// Computes average line length for standard input.
+import std.stdio;
+
+void main()
+{
+	ulong lines = 0;
+	double sumLength = 0;
+	foreach (line; stdin.byLine())
+	{
+		++lines;
+		sumLength += line.length;
+	}
+	writeln("Average line length: ",
+			lines ? sumLength / lines : 0);
+}
diff --git a/tests/frontpage.d.ref b/tests/frontpage.d.ref
new file mode 100644
index 0000000..654056d
--- /dev/null
+++ b/tests/frontpage.d.ref
@@ -0,0 +1,15 @@
+// Computes average line length for standard input.
+import std.stdio;
+
+void main()
+{
+    ulong lines = 0;
+    double sumLength = 0;
+    foreach (line; stdin.byLine())
+    {
+        ++lines;
+        sumLength += line.length;
+    }
+    writeln("Average line length: ", lines ? sumLength / lines:0);
+}
+
diff --git a/tests/hello.d b/tests/hello.d
new file mode 100644
index 0000000..f04ca6d
--- /dev/null
+++ b/tests/hello.d
@@ -0,0 +1 @@
+import std.stdio; void main() { writeln("Hello, world without explicit compilations!"); }
diff --git a/tests/hello.d.ref b/tests/hello.d.ref
new file mode 100644
index 0000000..3894114
--- /dev/null
+++ b/tests/hello.d.ref
@@ -0,0 +1,7 @@
+import std.stdio;
+
+void main()
+{
+    writeln("Hello, world without explicit compilations!");
+}
+
diff --git a/tests/test.sh b/tests/test.sh
new file mode 100755
index 0000000..ea46ff2
--- /dev/null
+++ b/tests/test.sh
@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+set -e
+
+for source in *.d
+do
+	../bin/dfmt "${source}" >"${source}.out"
+	diff -u "${source}.ref" "${source}.out" || echo "fail ${source}"
+done