Ensure that we have covered with tests some constants phpdoc checks

1. Constants have to be documented.
2. The @const tag is forbidden. Constants are documented with @var, if
   anything.

Note that this does not change anything in moodlecheck, but just covers
with tests the detection of undocumented constants and the (incorrect)
use of the @const tag.

Note that this is part of https://tracker.moodle.org/browse/MDL-77599

tests/fixtures/phpdoc_properties.php

@@ -24,6 +24,13 @@ class dummy_with_properties {
     var ?string $undocumented2;
     private $undocumented3;
     private ?string $undocumented4;
+    const UNDOCUMENTED_CONSTANT1 = 0;
+    public const UNDOCUMENTED_CONSTANT2 = 0;
+
+    /**
+     * @const A wrongly documented constant.
+     */
+    const WRONGLY_DOCUMENTED_CONSTANT = 0;
 
     /**
      * @var mixed $documented1 I'm just a dummy!
@@ -41,4 +48,9 @@ class dummy_with_properties {
      * @var ?string $documented4 I'm just a dummy!
      */
     private ?string $documented4;
+
+    /**
+     * @var A correctly documented constant.
+     */
+    const CORRECTLY_DOCUMENTED_CONSTANT = 0;
 }

tests/moodlecheck_rules_test.php

@@ -501,7 +501,7 @@ public function test_functionsdocumented_method_overrides() {
      * @covers ::local_moodlecheck_variablesdocumented
      * @covers \local_moodlecheck_file::get_variables
      */
-    public function test_variablesdocumented() {
+    public function test_variables_and_constants_documented() {
         $file = __DIR__ . "/fixtures/phpdoc_properties.php";
 
         global $PAGE;
@@ -515,6 +515,8 @@ public function test_variablesdocumented() {
 
         $xpath = new \DOMXpath($xmlresult);
 
+        // Verify that the undocumented variables are reported.
+
         $found = $xpath->query('//file/error[@source="variablesdocumented"]');
         // TODO: Change to DOMNodeList::count() when php71 support is gone.
         $this->assertSame(4, $found->length);
@@ -524,6 +526,24 @@ public function test_variablesdocumented() {
         $this->assertStringContainsString('$undocumented2', $found->item(1)->getAttribute("message"));
         $this->assertStringContainsString('$undocumented3', $found->item(2)->getAttribute("message"));
         $this->assertStringContainsString('$undocumented4', $found->item(3)->getAttribute("message"));
+
+        // Verify that the undocumented constants are reported.
+
+        $found = $xpath->query('//file/error[@source="constsdocumented"]');
+        // TODO: Change to DOMNodeList::count() when php71 support is gone.
+        $this->assertSame(2, $found->length);
+
+        // The PHPdocs of the other properties should be detected correctly.
+        $this->assertStringContainsString('UNDOCUMENTED_CONSTANT1', $found->item(0)->getAttribute("message"));
+        $this->assertStringContainsString('UNDOCUMENTED_CONSTANT2', $found->item(1)->getAttribute("message"));
+
+        // Verify that the @const tag is reported as invalid.
+
+        $found = $xpath->query('//file/error[@source="phpdocsinvalidtag"]');
+        // TODO: Change to DOMNodeList::count() when php71 support is gone.
+        $this->assertSame(1, $found->length);
+
+        $this->assertStringContainsString('Invalid phpdocs tag @const used', $found->item(0)->getAttribute("message"));
     }
 
     /**