diff --git a/go.mod b/go.mod
index eee059b..0274e76 100644
--- a/go.mod
+++ b/go.mod
@@ -1 +1,3 @@
 module gitlab.codemonkeysoftware.com/b/hatmill
+
+require github.com/leanovate/gopter v0.2.4
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..c19f72b
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+github.com/leanovate/gopter v0.2.4 h1:U4YLBggDFhJdqQsG4Na2zX7joVTky9vHaj/AGEwSuXU=
+github.com/leanovate/gopter v0.2.4/go.mod h1:gNcbPWNEWRe4lm+bycKqxUYoH5uoVje5SkOJ3uoLer8=
diff --git a/hatmill_test.go b/hatmill_test.go
new file mode 100644
index 0000000..4a0b82e
--- /dev/null
+++ b/hatmill_test.go
@@ -0,0 +1,47 @@
+package hatmill_test
+
+import (
+	"bytes"
+	"github.com/leanovate/gopter"
+	"github.com/leanovate/gopter/gen"
+	"github.com/leanovate/gopter/prop"
+	"gitlab.codemonkeysoftware.com/b/hatmill"
+	"testing"
+)
+
+type NopWriter struct{}
+
+func (NopWriter) Write(p []byte) (n int, err error) {
+	return len(p), nil
+}
+
+func TestText(t *testing.T) {
+	properties := gopter.NewProperties(nil)
+
+	properties.Property("writing to string is identity", prop.ForAll(
+		func(s string) bool {
+			var buf bytes.Buffer
+			hatmill.Text(s).WriteTo(&buf)
+			return buf.String() == s
+		},
+		gen.AnyString(),
+	))
+
+	properties.Property("WriteTo returns correct n", prop.ForAll(
+		func(s string) bool {
+			n, _ := hatmill.Text(s).WriteTo(NopWriter{})
+			return n == int64(len(s))
+		},
+		gen.AnyString(),
+	))
+
+	properties.Property("WriteTo does not generate error", prop.ForAll(
+		func(s string) bool {
+			_, err := hatmill.Text(s).WriteTo(NopWriter{})
+			return err == nil
+		},
+		gen.AnyString(),
+	))
+
+	properties.TestingRun(t)
+}