sshd/terminal: Import test from upstream patch

sshd/terminal/terminal_test.go

@@ -59,6 +59,7 @@ func TestClose(t *testing.T) {
 var keyPressTests = []struct {
 	in             string
 	line           string
+	received       string
 	err            error
 	throwAwayLines int
 }{
@@ -237,6 +238,49 @@ func TestKeyPresses(t *testing.T) {
 	}
 }
 
+var renderTests = []struct {
+	in       string
+	received string
+	err      error
+}{
+	{
+		// Cursor move after keyHome (left 4) then enter (right 4, newline)
+		in:       "abcd\x1b[H\r",
+		received: "> abcd\x1b[4D\x1b[4C\r\n",
+	},
+	{
+		// Write, home, prepend, enter. Prepends rewrites the line.
+		in: "cdef\x1b[Hab\r",
+		received: "> cdef" + // Initial input
+			"\x1b[4Da" + // Move cursor back, insert first char
+			"cdef" + // Copy over original string
+			"\x1b[4Dbcdef" + // Repeat for second char with copy
+			"\x1b[4D" + // Put cursor back in position to insert again
+			"\x1b[4C\r\n", // Put cursor at the end of the line and newline.
+	},
+}
+
+func TestRender(t *testing.T) {
+	for i, test := range renderTests {
+		for j := 1; j < len(test.in); j++ {
+			c := &MockTerminal{
+				toSend:       []byte(test.in),
+				bytesPerRead: j,
+			}
+			ss := NewTerminal(c, "> ")
+			_, err := ss.ReadLine()
+			if err != test.err {
+				t.Errorf("Error resulting from test %d (%d bytes per read) was '%v', expected '%v'", i, j, err, test.err)
+				break
+			}
+			if test.received != string(c.received) {
+				t.Errorf("Results rendered from test %d (%d bytes per read) was '%s', expected '%s'", i, j, c.received, test.received)
+				break
+			}
+		}
+	}
+}
+
 func TestPasswordNotSaved(t *testing.T) {
 	c := &MockTerminal{
 		toSend:       []byte("password\r\x1b[A\r"),