renames fixtures as testdata to avoid spurious dependencies (#359)

testdata/modifies-param.go

@@ -0,0 +1,25 @@
+package fixtures
+
+func one(a int) {
+	a, b := 1, 2 // MATCH /parameter 'a' seems to be modified/
+	a++          // MATCH /parameter 'a' seems to be modified/
+}
+
+func two(b, c float32) {
+	if c > 0.0 {
+		b = 1 // MATCH /parameter 'b' seems to be modified/
+	}
+}
+
+type foo struct {
+	a string
+}
+
+func three(s *foo) {
+	s.a = "foooooo"
+}
+
+// non regression test for issue 355
+func issue355(_ *foo) {
+	_ = "foooooo"
+}