Add test cases for branch coverage

* test/coverage/test_coverage.rb (test_branch_coverage_for_if_statement):
  Add test cases for modifier if/unless.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60365 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/coverage/test_coverage.rb

@@ -201,6 +201,8 @@ class TestCoverage < Test::Unit::TestCase
         [:unless,  3,  8, 2] => {[:else,  4, 11, 4]=>2, [:then,  5,  9, 4]=>1},
         [:if    ,  6, 14, 2] => {[:then,  7, 15, 4]=>2, [:else,  8, 14, 2]=>1},
         [:unless,  9, 18, 2] => {[:else, 10, 18, 2]=>2, [:then, 11, 19, 4]=>1},
+        [:if    , 12, 22, 2] => {[:then, 13, 22, 2]=>2, [:else, 14, 22, 2]=>1},
+        [:unless, 15, 23, 2] => {[:else, 16, 23, 2]=>2, [:then, 17, 23, 2]=>1},
       }
     }
     assert_coverage(<<~"end;", { branches: true }, result)
@@ -224,6 +226,9 @@ class TestCoverage < Test::Unit::TestCase
         unless x == 0
           0
         end
+
+        0 if x == 0
+        0 unless x == 0
       end
 
       foo(0)