Add test that surfaces issue with output containing invalid data

test/helloworld/go.mod

@@ -0,0 +1,13 @@
+module github.com/ActiveState/termtest/test/helloworld
+
+go 1.20
+
+replace github.com/ActiveState/termtest => ../../
+
+require github.com/ActiveState/termtest v0.0.0-00010101000000-000000000000
+
+require (
+	github.com/ActiveState/pty v0.0.0-20230628221854-6fb90eb08a14 // indirect
+	github.com/hinshun/vt10x v0.0.0-20220301184237-5011da428d02 // indirect
+	golang.org/x/sys v0.0.0-20220721230656-c6bc011c0c49 // indirect
+)

test/helloworld/go.sum

@@ -0,0 +1,11 @@
+github.com/ActiveState/pty v0.0.0-20230628221854-6fb90eb08a14 h1:RdhhSiwmgyUaaF2GBNrbqTwE5SM+MaVjwf91Ua+CK8c=
+github.com/ActiveState/pty v0.0.0-20230628221854-6fb90eb08a14/go.mod h1:5mM6vNRQwshCjlkOnVpwC//4ZpkiC6nmZr8lPOxJdXs=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/hinshun/vt10x v0.0.0-20220301184237-5011da428d02 h1:AgcIVYPa6XJnU3phs104wLj8l5GEththEw6+F79YsIY=
+github.com/hinshun/vt10x v0.0.0-20220301184237-5011da428d02/go.mod h1:Q48J4R4DvxnHolD5P8pOtXigYlRuPLGl6moFx3ulM68=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PKk=
+go.uber.org/goleak v1.2.0 h1:xqgm/S+aQvhWFTtR0XK3Jvg7z8kGV8P4X14IzwN3Eqk=
+golang.org/x/sys v0.0.0-20220721230656-c6bc011c0c49 h1:TMjZDarEwf621XDryfitp/8awEhiZNiwgphKlTMGRIg=
+golang.org/x/sys v0.0.0-20220721230656-c6bc011c0c49/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

test/helloworld/helloworld.go

@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("Hello World")
+}

test/helloworld/helloworld_test.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"testing"
+
+	"github.com/ActiveState/termtest"
+)
+
+func Test_ExactOutput(t *testing.T) {
+	_, filename, _, ok := runtime.Caller(0)
+	if !ok {
+		t.Fatal("unable to get the current filename")
+	}
+	cmd := exec.Command("go", "run", filepath.Join(filepath.Dir(filename), "helloworld.go"))
+
+	tt, err := termtest.New(cmd, termtest.OptTestErrorHandler(t))
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+
+	tt.ExpectExitCode(0)
+
+	output := tt.Output()
+	if output != "Hello World" {
+		t.Errorf("Output should be 'Hello World' and nothing else, got: %s", output)
+	}
+}