[lldb][NFC] Test going up/down one line in the multiline expression editor

lldb/packages/Python/lldbsuite/test/commands/expression/multiline-navigation/TestMultilineNavigation.py

@@ -0,0 +1,67 @@
+"""
+Tests navigating in the multiline expression editor.
+"""
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.lldbpexpect import PExpectTest
+
+class TestCase(PExpectTest):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    arrow_up = "\033[A"
+    arrow_down = "\033[B"
+
+    # PExpect uses many timeouts internally and doesn't play well
+    # under ASAN on a loaded machine..
+    @skipIfAsan
+    def test_nav_arrow_up(self):
+        """Tests that we can navigate back to the previous line with the up arrow"""
+        self.launch()
+
+        # Start multiline expression mode by just running 'expr'
+        self.child.sendline("expr")
+        self.child.expect_exact("terminate with an empty line to evaluate")
+        # Create a simple integer expression '123' and press enter.
+        self.child.send("123\n")
+        # We should see the prompt for the second line of our expression.
+        self.child.expect_exact("2: ")
+        # Go back to the first line and change 123 to 124.
+        # Then press enter twice to evaluate our expression.
+        self.child.send(self.arrow_up + "\b4\n\n")
+        # The result of our expression should be 124 (our edited expression)
+        # and not 123 (the one we initially typed).
+        self.child.expect_exact("(int) $0 = 124")
+
+        self.quit()
+
+    @skipIfAsan
+    def test_nav_arrow_down(self):
+        """Tests that we can navigate to the next line with the down arrow"""
+        self.launch()
+
+        # Start multiline expression mode by just running 'expr'
+        self.child.sendline("expr")
+        self.child.expect_exact("terminate with an empty line to evaluate")
+        # Create a simple integer expression '111' and press enter.
+        self.child.send("111\n")
+        # We should see the prompt for the second line of our expression.
+        self.child.expect_exact("2: ")
+        # Create another simple integer expression '222'.
+        self.child.send("222")
+        # Go back to the first line and change '111' to '111+' to make
+        # an addition operation that spans two lines. We need to go up to
+        # test that we can go back down again.
+        self.child.send(self.arrow_up + "+")
+        # Go back down to our second line and change '222' to '223'
+        # so that the full expression is now '111+\n223'.
+        # Then press enter twice to evaluate the expression.
+        self.child.send(self.arrow_down + "\b3\n\n")
+        # The result of our expression '111 + 223' should be '334'.
+        # If the expression is '333' then arrow down failed to get
+        # us back to the second line.
+        self.child.expect_exact("(int) $0 = 334")
+
+        self.quit()