Improve test coverage for the AssignmentInCondition sniff

This commit improves the test coverage for the AssignmentInCondition
sniff by adding a few more test case files to exercise the parts of the
sniff code that checks for invalid syntax.

Author: rodrigoprimo

src/Standards/Generic/Tests/CodeAnalysis/AssignmentInConditionUnitTest.2.inc

@@ -0,0 +1,4 @@
+<?php
+
+// Intentional parse error. Testing that the sniff is *not* triggered in this case.
+if ($a == 123

src/Standards/Generic/Tests/CodeAnalysis/AssignmentInConditionUnitTest.3.inc

@@ -0,0 +1,4 @@
+<?php
+
+// Intentional parse error. Testing that the sniff is *not* triggered in this case.
+for ($i = 0; $i == 100; $i++

src/Standards/Generic/Tests/CodeAnalysis/AssignmentInConditionUnitTest.4.inc

@@ -0,0 +1,6 @@
+<?php
+
+// Intentional parse error. Testing that the sniff is *not* triggered in this case.
+for ($i = 0) {
+    echo 'foo';
+}

src/Standards/Generic/Tests/CodeAnalysis/AssignmentInConditionUnitTest.5.inc

@@ -0,0 +1,6 @@
+<?php
+
+// Intentional parse error. Testing that the sniff is *not* triggered in this case.
+for ($i = 0; $i == 100) {
+    echo 'foo';
+}

src/Standards/Generic/Tests/CodeAnalysis/AssignmentInConditionUnitTest.6.inc

@@ -0,0 +1,5 @@
+<?php
+
+// Intentional parse error. Testing that the sniff is *not* triggered in this case.
+switch ( true ) {
+    case $sample == 'something'