C#: Add BMN tests for cs/constant-condition.

Author: michaelnebel

csharp/ql/test/query-tests/standalone/Bad Practices/Control-Flow/ConstantCondition/ConstantCondition.cs

@@ -0,0 +1,27 @@
+using System;
+
+partial class C1
+{
+    public C2 Prop { get; set; }
+}
+
+class C2 { }
+
+class ConstantMatching
+{
+    void M1()
+    {
+        var c1 = new C1();
+        if (c1.Prop is int) // $ Alert
+        {
+        }
+
+        // Should not be considered a constant condition as
+        // we don't know anything about D.
+        var d = new D();
+        if (d.Prop is C2) // $ Alert
+        {
+        }
+    }
+}
+

csharp/ql/test/query-tests/standalone/Bad Practices/Control-Flow/ConstantCondition/ConstantCondition.expected

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+| ConstantCondition.cs:15:13:15:26 | ... is ... | Condition always evaluates to 'false'. |
+| ConstantCondition.cs:15:24:15:26 | access to type Int32 | Pattern never matches. |
+| ConstantCondition.cs:22:13:22:24 | ... is ... | Condition always evaluates to 'false'. |
+| ConstantCondition.cs:22:23:22:24 | access to type C2 | Pattern never matches. |

csharp/ql/test/query-tests/standalone/Bad Practices/Control-Flow/ConstantCondition/ConstantCondition.qlref

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+query: Bad Practices/Control-Flow/ConstantCondition.ql
+postprocess: utils/test/InlineExpectationsTestQuery.ql

csharp/ql/test/query-tests/standalone/Bad Practices/Control-Flow/ConstantCondition/options

@@ -0,0 +1 @@
+semmle-extractor-options: --standalone