[lldb][NFC] Add more tests for GenerateOptionsUsage

[DavidSpickett]

Summary

This adds a few targeted tests to make sure that when refactoring
this function later I don't break these properties.

Some are tested in passing elsewhere but this makes it more
obvious what went wrong when it fails.

This doesn't cover everything the function does, I couldn't
find any examples that would exercise some of the code.

[DavidSpickett]

@jingham You suggested I take a look at this function after I did a small fix a while back so adding you on review for this and the following changes.

[DavidSpickett]

Ping!

[DavidSpickett]

I realised that in theory the tests could still pass if your ordering
just happend to land in the right way.

For the short option [-ABCabc] there's not a lot I can do about that,
so I added another check for a different command. More chance to catch
non-determinism. I don't think any commands have enough options to make
it 100% sure.

For the detailed options I switched from a regex to cutting up the
output with python. Then once we've got all the short names we can
check the whole order.

(and I checked, when it fails you do get a list specific comparison output)

[jingham]

Ah, tests for help that I asked for in another review... Excellent.

lldb/test/API/commands/help/TestHelp.py

def test_help_option_group_format_options_usage(self):
 
         self.expect(
             "help memory write",
             matching=True,
             substrs=[
                 "-f <format> ( --format <format> )", "The format to use for each of the value to be written.",
                 "-s <byte-size> ( --size <byte-size> )", "The size in bytes to write from input file or each value."])
 
+    @no_debug_info_test
+    def test_help_shows_optional_short_options(self):
+        """Test that optional short options are printed and that they are in
+           alphabetical order with upper case options first."""
+        self.expect("help memory read",
+                    substrs=["memory read [-br]", "memory read [-AFLORTr]"])
+
+    @no_debug_info_test
+    def test_help_shows_command_options_usage(self):
+        """Test that we start the usage section with a specific line."""
+        self.expect("help memory read", substrs=["Command Options Usage:\n  memory read"])
+
+    @no_debug_info_test
+    def test_help_detailed_information_spacing(self):
+        """Test that we put a break between the usage and the options help lines,
+           and between the options themselves."""
+        self.expect("help memory read", substrs=[
+                    "[<address-expression>]\n\n       --show-tags",
+                    # Starts with the end of the show-tags line
+                    "output).\n\n       -A"])
+
+    @no_debug_info_test
+    def test_help_detailed_information_ordering(self):
+        """Test that we order options alphabetically, upper case first."""
+        self.expect("help memory read", patterns=[
+            "(?s)\-L \( \-\-location \).*\-T \( \-\-show\-types \).*"
+                "\-b \( \-\-binary \).*\-r \( \-\-force \)"])
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