ruby: add tests

ruby/ql/test/query-tests/variables/DeadStoreOfLocal/DeadStoreOfLocal.rb

@@ -0,0 +1,36 @@
+def test_basic(x)
+    y = x  #$ Alert
+    y = x + 2
+    return y
+end
+
+def test_retry
+    x = 0
+    begin
+        if x == 0
+            raise "error"
+        end
+    rescue
+        x = 2  #$ SPURIOUS: Alert
+        retry
+    end
+    return 42
+end
+
+def test_binding
+    x = 4  #$ SPURIOUS: Alert
+    return binding
+end
+
+class Sup
+    def m(x)
+        print(x + 1)
+    end
+end
+  
+class Sub < Sup
+    def m(y)
+        y = 3  # OK - the call to `super` sees the value of y
+        super
+    end
+end