junit: fix invalid XML for param tests with strs

Fix a bug where the JUnit reporter generated invalid XML for
parameterized tests with string arguments.

Closes #407

Author: mandesero

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Fix a bug when the JUnit reporter generating invalid XML for parameterized
+  tests with string arguments (gh-407).
 - Group and suite hooks must now be registered using the call-style
   API. Use:
 

luatest/output/junit.lua

@@ -99,7 +99,7 @@ function Output.mt:end_suite()
 
     for _, node in ipairs(self.result.tests.all) do
         self.fd:write(string.format('        <testcase group="%s" name="%s" time="%0.3f">\n',
-            node.group.name or '', node.name, node.duration))
+            Output.xml_escape(node.group.name or ''), Output.xml_escape(node.name or ''), node.duration))
         if not node:is('success') then
             self.fd:write(self.class.node_status_xml(node))
         end

test/luaunit/utility_test.lua

@@ -2,6 +2,7 @@ local t = require('luatest')
 local g = t.group()
 
 local fun = require('fun')
+local fio = require('fio')
 local Runner = require('luatest.runner')
 local utils = require('luatest.utils')
 
@@ -786,6 +787,45 @@ function g.test_xml_c_data_escape()
     t.assert_equals(subject("a<b]]>--"), 'a<b]]&gt;--')
 end
 
+function g.test_junit_output_escape_for_attributes()
+    local tmpdir = fio.tempdir()
+    local output_path = fio.pathjoin(tmpdir, 'test_junit_escape')
+
+    t.assert_equals(helper.run_suite(function(lu2)
+        local g_positive_start_stages = lu2.group('touching_positive.start.stages', {
+            { stage = 'COMPLETED' },
+            { stage = 'CANCELLED' },
+        })
+
+        function g_positive_start_stages.test_start() end
+    end, {'-o', 'junit', '-n', output_path}), 0)
+
+    local file = assert(io.open(output_path .. '.xml'))
+    local xml = file:read('*a')
+    file:close()
+
+    t.assert_str_contains(
+        xml,
+        'group="touching_positive.start.stages.stage:&quot;COMPLETED&quot;"'
+    )
+    t.assert_str_contains(
+        xml,
+        'name="touching_positive.start.stages.stage:&quot;COMPLETED&quot;.test_start"'
+    )
+
+    t.assert_str_contains(
+        xml,
+        'group="touching_positive.start.stages.stage:&quot;CANCELLED&quot;"'
+    )
+    t.assert_str_contains(
+        xml,
+        'name="touching_positive.start.stages.stage:&quot;CANCELLED&quot;.test_start"'
+    )
+
+    fio.rmtree(tmpdir)
+end
+
+
 function g.test_stripStackTrace()
     local subject = utils.strip_luatest_trace