diff --git a/gigaparsec.go b/gigaparsec.go
index 5762d41..19e20de 100644
--- a/gigaparsec.go
+++ b/gigaparsec.go
@@ -48,6 +48,13 @@ func (s State[T]) Pos() uint64 {
 	return s.cursor.Pos()
 }
 
+func Parse[In, Out any](p Parser[In, Out], c cursor.Cursor[In]) (result Out, err error) {
+	st := State[In]{cursor: c}
+	var reply Result[In, Out]
+	_, reply, err = p(st)
+	return reply.Value, err
+}
+
 type Parser[In, Out any] func(State[In]) (consumed bool, reply Result[In, Out], err error)
 
 func Return[In, Out any](value Out) Parser[In, Out] {
diff --git a/go.mod b/go.mod
index ba08155..53000a0 100644
--- a/go.mod
+++ b/go.mod
@@ -8,3 +8,5 @@ require (
 )
 
 require github.com/google/go-cmp v0.6.0 // indirect
+
+replace github.com/shoenig/test v1.10.0 => ../shoenig-test
diff --git a/parser_test.go b/parser_test.go
new file mode 100644
index 0000000..74c6409
--- /dev/null
+++ b/parser_test.go
@@ -0,0 +1,52 @@
+package gigaparsec_test
+
+import (
+	"bytes"
+	"testing"
+
+	"git.codemonkeysoftware.net/b/gigaparsec"
+	"git.codemonkeysoftware.net/b/gigaparsec/cursor"
+	"github.com/shoenig/test"
+	"pgregory.net/rapid"
+)
+
+func Todo(t *testing.T) {
+	t.Errorf("TODO")
+}
+
+func notP[T any](pred func(T) bool) func(T) bool {
+	return func(x T) bool { return !pred(x) }
+}
+
+func hasPrefix(prefix []byte) func([]byte) bool {
+	return func(b []byte) bool { return bytes.HasPrefix(b, prefix) }
+}
+
+func TestSlice(t *testing.T) {
+	t.Run("fails with wrong contents", rapid.MakeCheck(func(t *rapid.T) {
+		s := rapid.SliceOfN(rapid.Byte(), 1, -1).Draw(t, "s")
+		input := rapid.SliceOfN(rapid.Byte(), len(s), -1).
+			Filter(notP(hasPrefix(s))).Draw(t, "input")
+		out, err := gigaparsec.Parse(gigaparsec.Slice(s), cursor.NewSlice(input))
+		test.ErrorAs(t, err, &gigaparsec.ParseError{})
+		test.SliceEmpty(t, out)
+	}))
+	t.Run("fails at end of input", rapid.MakeCheck(func(t *rapid.T) {
+		s := rapid.SliceOfN(rapid.Byte(), 1, -1).Draw(t, "s")
+		inputLen := rapid.IntRange(0, len(s)-1).Draw(t, "inputLen")
+		input := s[:inputLen]
+		out, err := gigaparsec.Parse(gigaparsec.Slice(s), cursor.NewSlice(input))
+		test.ErrorAs(t, err, &gigaparsec.ParseError{})
+		test.SliceEmpty(t, out)
+	}))
+	t.Run("fails when read fails", Todo)
+	t.Run("succeeds when contents match", rapid.MakeCheck(func(t *rapid.T) {
+		input := rapid.SliceOfN(rapid.Byte(), 1, -1).Draw(t, "input")
+		sLen := rapid.IntRange(0, len(input)).Draw(t, "sLen")
+		s := input[:sLen]
+		out, err := gigaparsec.Parse(gigaparsec.Slice(s), cursor.NewSlice(input))
+		test.NoError(t, err)
+		test.SliceEqOp(t, s, out)
+	}))
+	t.Run("next state has correct position", Todo)
+}