[lldb][NFC] Refactor TestCallBuiltinFunction

Using asserts doesn't print a useful error message in case this test fails.

llvm-svn: 372815
diff --git a/lldb/packages/Python/lldbsuite/test/commands/expression/call-function/TestCallBuiltinFunction.py b/lldb/packages/Python/lldbsuite/test/commands/expression/call-function/TestCallBuiltinFunction.py
index 87787f3..0065d98 100644
--- a/lldb/packages/Python/lldbsuite/test/commands/expression/call-function/TestCallBuiltinFunction.py
+++ b/lldb/packages/Python/lldbsuite/test/commands/expression/call-function/TestCallBuiltinFunction.py
@@ -40,14 +40,7 @@
 
         # Test different builtin functions.
 
-        interp.HandleCommand("expr __builtin_isinf(0.0f)", result)
-        self.assertEqual(result.GetOutput(), "(int) $0 = 0\n")
-
-        interp.HandleCommand("expr __builtin_isnormal(0.0f)", result)
-        self.assertEqual(result.GetOutput(), "(int) $1 = 0\n")
-
-        interp.HandleCommand("expr __builtin_constant_p(1)", result)
-        self.assertEqual(result.GetOutput(), "(int) $2 = 1\n")
-
-        interp.HandleCommand("expr __builtin_abs(-14)", result)
-        self.assertEqual(result.GetOutput(), "(int) $3 = 14\n")
+        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"])