test: Class to test all fmt

coverage.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" ?>
-<coverage version="6.3.1" timestamp="1644493279412" lines-valid="3607" lines-covered="3532" line-rate="0.9792" branches-covered="0" branches-valid="0" branch-rate="0" complexity="0">
+<coverage version="6.3.1" timestamp="1644493525824" lines-valid="3611" lines-covered="3536" line-rate="0.9792" branches-covered="0" branches-valid="0" branch-rate="0" complexity="0">
 	<!-- Generated by coverage.py: https://coverage.readthedocs.io -->
 	<!-- Based on https://raw.githubusercontent.com/cobertura/web/master/htdocs/xml/coverage-04.dtd -->
 	<sources>
@@ -634,6 +634,10 @@
 						<line number="92" hits="1"/>
 						<line number="93" hits="1"/>
 						<line number="96" hits="1"/>
+						<line number="98" hits="1"/>
+						<line number="102" hits="1"/>
+						<line number="103" hits="1"/>
+						<line number="104" hits="1"/>
 					</lines>
 				</class>
 				<class name="test_linter.py" filename="tests/test_linter.py" complexity="0" line-rate="1" branch-rate="0">

tests/test_format.py

@@ -16,9 +16,6 @@ from yamllint.format import (
 )
 
 
-INPUT = []
-
-
 class TextToXMLTestCase(unittest.TestCase):
 
     specials = {
@@ -91,3 +88,17 @@ class FormaterTestCase(unittest.TestCase):
             inst.show_problems_for_file([], "a")
         with self.assertRaises(NotImplementedError):
             inst.show_problem(None, "a")
+
+
+class FormatersTestCase(unittest.TestCase):
+
+    args = [
+        (ParsableFormater(True), {"file1.yml": []}, ""),
+    ]
+
+    def test_all_formaters(self):
+        for inst, inp, ret in self.args:
+            self.assertEqual(
+                inst.show_problems_for_all_files(inp),
+                ret
+            )

yamllint/format.py

@@ -381,7 +381,11 @@ class CodeclimateFormater(Formater):
 
 def max_level(all_problems):
     """Return the max level of all problems."""
-    all_levels = [problem.level for problems in all_problems.values() for problem in problems]
+    all_levels = [
+        problem.level
+        for problems in all_problems.values()
+        for problem in problems
+    ]
     if all_levels:
         return max(map(lambda x: PROBLEM_LEVELS[x], all_levels))
     return 0