check_test_cases: Unify walk_compat_sh and walk_opt_sh into one

walk_compat_sh and walk_opt_sh are basically the same now, so:

 * Merge them into one function.
 * Use the --list-test-cases option for both of them.
 * Rename this merged function as collect_from_script which seems
   more appropriate as since it isn't iterating the script but
   calling it.

Signed-off-by: Tomás González <tomasagustin.gonzalezorlando@arm.com>
diff --git a/tests/scripts/check_test_cases.py b/tests/scripts/check_test_cases.py
index 4301b32..2dddf7a 100755
--- a/tests/scripts/check_test_cases.py
+++ b/tests/scripts/check_test_cases.py
@@ -27,7 +27,6 @@
 import re
 import subprocess
 import sys
-import subprocess
 
 
 class Results:
@@ -99,26 +98,18 @@
                                            data_file_name, line_number, line)
                 in_paragraph = True
 
-    def walk_ssl_opt_sh(self, file_name):
-        """Iterate over the test cases in ssl-opt.sh or a file with a similar format."""
+    def collect_from_script(self, file_name):
+        """Collect the test cases in a script by calling its listing test cases
+option"""
         descriptions = self.new_per_file_state() # pylint: disable=assignment-from-none
-        listed = subprocess.check_output([file_name, '-l'])
+        listed = subprocess.check_output(['sh', file_name, '--list-test-cases'])
+        # Assume test file is responsible for printing identical format of
+        # test case description between --list-test-cases and its OUTCOME.CSV
         listed = set(map(lambda x: x.rstrip(), listed.splitlines()))
-        for description in listed:
-            self.process_test_case(descriptions, file_name, None, description)
-
-    def walk_compat_sh(self, file_name):
-        """Iterate over the test cases compat.sh with a similar format."""
-        descriptions = self.new_per_file_state() # pylint: disable=assignment-from-none
-        compat_cmd = ['sh', file_name, '--list-test-case']
-        compat_output = subprocess.check_output(compat_cmd)
-        # Assume compat.sh is responsible for printing identical format of
-        # test case description between --list-test-case and its OUTCOME.CSV
-        description = compat_output.strip().split(b'\n')
         # idx indicates the number of test case since there is no line number
         # in `compat.sh` for each test case.
-        for idx, descrip in enumerate(description):
-            self.process_test_case(descriptions, file_name, idx, descrip)
+        for idx, description in enumerate(listed):
+            self.process_test_case(descriptions, file_name, idx, description)
 
     @staticmethod
     def collect_test_directories():
@@ -139,12 +130,11 @@
             for data_file_name in glob.glob(os.path.join(directory, 'suites',
                                                          '*.data')):
                 self.walk_test_suite(data_file_name)
-            ssl_opt_sh = os.path.join(directory, 'ssl-opt.sh')
-            if os.path.exists(ssl_opt_sh):
-                self.walk_ssl_opt_sh(ssl_opt_sh)
-            compat_sh = os.path.join(directory, 'compat.sh')
-            if os.path.exists(compat_sh):
-                self.walk_compat_sh(compat_sh)
+
+            for sh_file in ['ssl-opt.sh', 'compat.sh']:
+                sh_file = os.path.join(directory, sh_file)
+                if os.path.exists(sh_file):
+                    self.collect_from_script(sh_file)
 
 class TestDescriptions(TestDescriptionExplorer):
     """Collect the available test cases."""