pkg/program/shell: Test against Interact.

This addresses #944.

pkg/program/shell/interact_test.go

@@ -9,6 +9,55 @@ import (
 	"github.com/elves/elvish/pkg/eval/vars"
 )
 
+func TestInteract_SingleCommand(t *testing.T) {
+	f := setup()
+	defer f.cleanup()
+	f.feedIn("echo hello\n")
+
+	Interact(f.fds(), &InteractConfig{})
+	f.testOut(t, 1, "hello\n")
+}
+
+func TestInteract_Exception(t *testing.T) {
+	f := setup()
+	defer f.cleanup()
+	f.feedIn("fail mock\n")
+
+	Interact(f.fds(), &InteractConfig{})
+	f.testOutSnippet(t, 2, "fail mock")
+}
+
+func TestInteract_RcFile(t *testing.T) {
+	f := setup()
+	defer f.cleanup()
+	f.feedIn("")
+
+	writeFile("rc.elv", "echo hello from rc.elv")
+
+	Interact(f.fds(), &InteractConfig{Paths: Paths{Rc: "rc.elv"}})
+	f.testOut(t, 1, "hello from rc.elv\n")
+}
+
+func TestInteract_RcFile_Exception(t *testing.T) {
+	f := setup()
+	defer f.cleanup()
+	f.feedIn("")
+
+	writeFile("rc.elv", "fail mock")
+
+	Interact(f.fds(), &InteractConfig{Paths: Paths{Rc: "rc.elv"}})
+	f.testOutSnippet(t, 2, "fail mock")
+}
+
+func TestInteract_RcFile_NonexistentIsOK(t *testing.T) {
+	f := setup()
+	defer f.cleanup()
+	f.feedIn("")
+
+	Interact(f.fds(), &InteractConfig{Paths: Paths{Rc: "rc.elv"}})
+	f.testOut(t, 1, "")
+}
+
 func TestExtractExports(t *testing.T) {
 	ns := eval.Ns{
 		exportsVarName: vars.NewReadOnly(vals.EmptyMap.Assoc("a", "lorem")),

pkg/program/shell/testutil_test.go

@@ -30,6 +30,14 @@ func (f *fixture) fds() [3]*os.File {
 	return [3]*os.File{f.pipes[0].r, f.pipes[1].w, f.pipes[2].w}
 }
 
+func (f *fixture) feedIn(s string) {
+	_, err := f.pipes[0].w.WriteString(s)
+	if err != nil {
+		panic(err)
+	}
+	f.pipes[0].w.Close()
+}
+
 func (f *fixture) testOut(t *testing.T, fd int, wantOut string) {
 	t.Helper()
 	if out := f.pipes[fd].get(); out != wantOut {