1 files changed, 80 insertions, 0 deletions
diff --git a/src/common/testsupport.h b/src/common/testsupport.h
new file mode 100644
index 0000000000..4a4f50b69b
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+++ b/src/common/testsupport.h
@@ -0,0 +1,80 @@
+/* Copyright (c) 2013, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#ifndef TOR_TESTSUPPORT_H
+#define TOR_TESTSUPPORT_H
+
+#ifdef TOR_UNIT_TESTS
+#define STATIC
+#else
+#define STATIC static
+#endif
+
+/** Quick and dirty macros to implement test mocking.
+ *
+ * To use them, suppose that you have a function you'd like to mock
+ * with the signature "void writebuf(size_t n, char *buf)".  You can then
+ * declare the function as:
+ *
+ *     MOCK_DECL(void, writebuf, (size_t n, char *buf));
+ *
+ * and implement it as:
+ *
+ *     MOCK_IMPL(void
+ *     writebuf,(size_t n, char *buf)
+ *     {
+ *          ...
+ *     }
+ *
+ * For the non-testing build, this will expand simply into:
+ *
+ *     void writebuf(size_t n, char *buf);
+ *     void
+ *     writebuf(size_t n, char *buf)
+ *     {
+ *         ...
+ *     }
+ *
+ * But for the testing case, it will expand into:
+ *
+ *     void writebuf__real(size_t n, char *buf);
+ *     extern void (*writebuf)(size_t n, char *buf);
+ *
+ *     void (*writebuf)(size_t n, char *buf) = writebuf__real;
+ *     void
+ *     writebuf__real(size_t n, char *buf)
+ *     {
+ *         ...
+ *     }
+ *
+ * This is not a great mocking system!  It is deliberately "the simplest
+ * thing that could work", and pays for its simplicity in its lack of
+ * features, and in its uglification of the Tor code.  Replacing it with
+ * something clever would be a fine thing.
+ *
+ * @{ */
+#ifdef TOR_UNIT_TESTS
+#define MOCK_DECL(rv, funcname, arglist)     \
+  rv funcname ##__real arglist;              \
+  extern rv(*funcname) arglist
+#define MOCK_IMPL(rv, funcname, arglist)     \
+  rv(*funcname) arglist = funcname ##__real; \
+  rv funcname ##__real arglist
+#define MOCK(func, replacement)                 \
+  do {                                          \
+    (func) = (replacement);                     \
+  } while (0)
+#define UNMOCK(func)                            \
+  do {                                          \
+    func = func ##__real;                       \
+  } while (0)
+#else
+#define MOCK_DECL(rv, funcname, arglist) \
+  rv funcname arglist
+#define MOCK_IMPL(rv, funcname, arglist) \
+  rv funcname arglist
+#endif
+/** @} */
+
+#endif
+