testscript: minor updates to Setenv logic (#98)

- include the key in the panic message
- cosmetic improvements to tests

Author: rogpeppe

testscript/testscript.go

@@ -85,7 +85,7 @@ func (e *Env) Getenv(key string) string {
 // panics if key is invalid.
 func (e *Env) Setenv(key, value string) {
 	if key == "" || strings.IndexByte(key, '=') != -1 {
-		panic("Setenv: invalid argument")
+		panic(fmt.Errorf("invalid environment variable key %q", key))
 	}
 	e.Vars = append(e.Vars, key+"="+value)
 }

testscript/testscript_test.go

@@ -99,32 +99,31 @@ func TestEnv(t *testing.T) {
 
 	e.Setenv("HOME", "/home/user")
 	if got, want := e.Getenv("HOME"), "/home/user"; got != want {
-		t.Errorf("e.Getenv(\"HOME\") == %q, want %q", got, want)
+		t.Errorf(`e.Getenv("HOME") == %q, want %q`, got, want)
 	}
 
 	if got, want := e.Getenv("PATH"), "/usr/bin:/usr/local/bin"; got != want {
-		t.Errorf("e.Getenv(\"PATH\") == %q, want %q", got, want)
+		t.Errorf(`e.Getenv("PATH") == %q, want %q`, got, want)
 	}
 
 	if got, want := e.Getenv("INVALID"), ""; got != want {
-		t.Errorf("e.Getenv(\"INVALID\") == %q, want %q", got, want)
+		t.Errorf(`e.Getenv("INVALID") == %q, want %q`, got, want)
 	}
 
 	for _, key := range []string{
 		"",
 		"=",
 		"key=invalid",
 	} {
-		value := ""
 		var panicValue interface{}
 		func() {
 			defer func() {
 				panicValue = recover()
 			}()
-			e.Setenv(key, value)
+			e.Setenv(key, "")
 		}()
 		if panicValue == nil {
-			t.Errorf("e.Setenv(%q, %q) did not panic, want panic", key, value)
+			t.Errorf("e.Setenv(%q) did not panic, want panic", key)
 		}
 	}
 }