diff --git a/bytes/regexp_test.go b/bytes/regexp_test.go
index 11f3953..6c77b92 100644
--- a/bytes/regexp_test.go
+++ b/bytes/regexp_test.go
@@ -4,6 +4,7 @@ package bytes_test
 
 import (
 	"bytes"
+	"errors"
 	"strings"
 	"testing"
 
@@ -21,20 +22,43 @@ func Todo(t *testing.T) {
 }
 
 func TestRegexp(t *testing.T) {
-	t.Run("only searches the beginning of input", Todo)
-	t.Run("position is correct after match", Todo)
-	t.Run("fails on unexpected error", Todo)
-	t.Run("returns a useful Got value", rapid.MakeCheck(func(t *rapid.T) {
+	alpha := rapid.SliceOfBytesMatching(`[A-Za-z]{1,100}`)
+	t.Run("position and value are correct after match", rapid.MakeCheck(func(t *rapid.T) {
+		needle := alpha.Draw(t, "needle")
+		input := rapid.Map(alpha, func(suffix []byte) []byte { return append(needle, suffix...) }).
+			Draw(t, "input")
+
+		p := pbytes.Regexp(string(needle))
+		result, err := p(gigaparsec.MakeState(bytes.NewReader(input)))
+		succeeded, val, next := result.Status()
 
-	}))
-	t.Run("basically works", func(t *testing.T) {
-		result, err := pbytes.Regexp("a")(gigaparsec.MakeState(strings.NewReader("a")))
 		must.NoError(t, err)
-		success, value, _ := result.Status()
-		test.True(t, success, test.Sprint(result.Message()))
-		test.EqOp(t, "a", value)
-		test.True(t, result.Consumed())
+		test.True(t, succeeded)
+		test.EqOp(t, string(needle), val)
+		ptest.StateIsAt(t, next, uint64(len(needle)))
+	}))
+	t.Run("only searches the beginning of input", rapid.MakeCheck(func(t *rapid.T) {
+		needle := alpha.Draw(t, "needle")
+		input := rapid.Map(alpha, func(prefix []byte) []byte { return append(prefix, needle...) }).
+			Filter(func(b []byte) bool { return !bytes.HasPrefix(b, needle) }).
+			Draw(t, "input")
+
+		p := pbytes.Regexp(string(needle))
+		result, err := p(gigaparsec.MakeState(bytes.NewReader(input)))
+		succeeded, _, _ := result.Status()
+
+		must.NoError(t, err)
+		test.False(t, succeeded)
+	}))
+	t.Run("fails on unexpected error", func(t *testing.T) {
+		expectedErr := errors.New("it broke")
+		p := pbytes.Regexp("nope")
+		result, err := p(gigaparsec.MakeState(ptest.ErrReaderAt(expectedErr)))
+		succeeded, _, _ := result.Status()
+		test.ErrorIs(t, err, expectedErr)
+		test.False(t, succeeded)
 	})
+	t.Run("returns a useful Got value", Todo)
 }
 
 func TestRuneReader(t *testing.T) {