Index: lldb/packages/Python/lldbsuite/test/commands/expression/call-function/TestCallBuiltinFunction.py
===================================================================
--- lldb/packages/Python/lldbsuite/test/commands/expression/call-function/TestCallBuiltinFunction.py
+++ lldb/packages/Python/lldbsuite/test/commands/expression/call-function/TestCallBuiltinFunction.py
@@ -39,7 +39,7 @@
 
         # Test different builtin functions.
 
-        self.expect("expr __builtin_isinf(0.0f)", substrs=["(int) $", " = 0\n"])
-        self.expect("expr __builtin_isnormal(0.0f)", substrs=["(int) $", " = 0\n"])
-        self.expect("expr __builtin_constant_p(1)", substrs=["(int) $", " = 1\n"])
-        self.expect("expr __builtin_abs(-14)", substrs=["(int) $", " = 14\n"])
+        self.expect_expr("__builtin_isinf(0.0f)", result_type="int", result_value="0")
+        self.expect_expr("__builtin_isnormal(0.0f)", result_type="int", result_value="0")
+        self.expect_expr("__builtin_constant_p(1)", result_type="int", result_value="1")
+        self.expect_expr("__builtin_abs(-14)", result_type="int", result_value="144")
Index: lldb/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/string/TestDataFormatterLibcxxString.py
===================================================================
--- lldb/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/string/TestDataFormatterLibcxxString.py
+++ lldb/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/string/TestDataFormatterLibcxxString.py
@@ -96,10 +96,11 @@
             cappedSummary.find("someText") <= 0,
             "cappedSummary includes the full string")
 
+        self.expect_expr("s", result_type=ns+"::wstring", result_summary='L"hello world! מזל טוב!"')
+
         self.expect(
             "frame variable",
             substrs=[
-                '(%s::wstring) s = L"hello world! מזל טוב!"'%ns,
                 '(%s::wstring) S = L"!!!!!"'%ns,
                 '(const wchar_t *) mazeltov = 0x',
                 'L"מזל טוב"',
Index: lldb/packages/Python/lldbsuite/test/lldbtest.py
===================================================================
--- lldb/packages/Python/lldbsuite/test/lldbtest.py
+++ lldb/packages/Python/lldbsuite/test/lldbtest.py
@@ -2366,6 +2366,71 @@
         self.assertTrue(matched if matching else not matched,
                         msg if msg else EXP_MSG(str, output, exe))
 
+    def expect_expr(
+            self,
+            expr,
+            result_summary=None,
+            result_value=None,
+            result_type=None,
+            error_msg=None,
+            ):
+        """
+        Evaluates the given expression and verifies the result.
+        :param expr: The expression as a string.
+        :param result_summary: The summary that the expression should have. None if the summary should not be checked.
+        :param result_value: The value that the expression should have. None if the value should not be checked.
+        :param result_type: The type that the expression result should have. None if the type should not be checked.
+        :param error_msg: The error message the expression should return. None if the error output should not be checked.
+
+        result_summary, result_value, result_type and error_message can have the following types which influences how
+        their values are compared to their respective output:
+          * A list of strings: expect_expr will search for the list of strings in the respective output.
+                               The output is expected to contain these strings in the listed order.
+          * Any string type: expect_expr will assume that the respective output is equal to the given string.
+        """
+        # Utility method that checks result_value, result_type and error_message.
+        def check_str(outer_self, expected, got):
+            self.assertIsNotNone(expected)
+            self.assertIsNotNone(got)
+            # We got a list, so treat is as a list of needles we need to find in the given order.
+            if type(expected) is list:
+                remaining = got
+                for expected_part in expected:
+                    # Find the expected string.
+                    i = remaining.find(expected_part)
+                    # Assert that we found the string.
+                    outer_self.assertTrue(i != -1, "Couldn't find '" + expected_part
+                                          + "' in remaining output '" + remaining +
+                                          "'.\nFull string was: '" + got + "'")
+                    # Keep searching only the rest of the string to ensure the
+                    # strings are found in the given order.
+                    remaining = remaining[i + len(expected_part):]
+            else: # Otherwise we probably got one of Python's many string classes.
+                outer_self.assertEqual(got, expected)
+
+        self.assertTrue(expr.strip() == expr, "Expression contains trailing/leading whitespace: '" + expr + "'")
+
+        frame = self.dbg.GetTargetAtIndex(0).GetProcess().GetThreadAtIndex(0).GetFrameAtIndex(0)
+        eval_result = frame.EvaluateExpression(expr)
+
+        if error_msg:
+            self.assertFalse(eval_result.IsValid())
+            check_str(self, error_msg, eval_result.GetError().GetCString())
+            return
+
+        if not eval_result.GetError().Success():
+            self.assertTrue(eval_result.GetError().Success(),
+                "Unexpected failure with msg: " + eval_result.GetError().GetCString())
+
+        if result_type:
+            check_str(self, result_type, eval_result.GetTypeName())
+
+        if result_value:
+            check_str(self, result_value, eval_result.GetValue())
+
+        if result_summary:
+            check_str(self, result_summary, eval_result.GetSummary())
+
     def invoke(self, obj, name, trace=False):
         """Use reflection to call a method dynamically with no argument."""
         trace = (True if traceAlways else trace)