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+c-ares Unit Test Suite
+======================
+
+
+This directory holds unit tests for the c-ares library.  To build the tests:
+
+ - Build the main c-ares library first, in the directory above this.  To
+   enable tests of internal functions, configure the library build to expose
+   hidden symbols with `./configure --disable-symbol-hiding`.
+ - Generate a `configure` file by running `autoreconf -iv` (which requires
+   a local installation of
+   [autotools](https://www.gnu.org/software/automake/manual/html_node/Autotools-Introduction.html)).
+ - `./configure`
+ - `make`
+ - Run the tests with `./arestest`, or `./arestest -v` for extra debug info.
+
+Points to note:
+
+ - The tests are written in C++11, and so need a C++ compiler that supports
+   this.  To avoid adding this as a requirement for the library, the
+   configuration and build of the tests is independent from the library.
+ - The tests include some live queries, which will fail when run on a machine
+   without internet connectivity.  To skip live tests, run with
+   `./arestest --gtest_filter=-*.Live*`.
+ - The tests include queries of a mock DNS server.  This server listens on port
+   5300 by default, but the port can be changed with the `-p 5300` option to
+   `arestest`.
+
+
+Test Types
+----------
+
+The test suite includes various different types of test.
+
+ - There are live tests (`ares-test-live.cc`), which assume that the
+   current machine has a valid DNS setup and connection to the
+   internet; these tests issue queries for real domains but don't
+   particularly check what gets returned.  The tests will fail on
+   an offline machine.
+ - There are some mock tests (`ares-test-mock.cc`) that set up a fake DNS
+   server and inject its port into the c-ares library configuration.
+   These tests allow specific response messages to be crafted and
+   injected, and so are likely to be used for many more tests in
+   future.
+    - To make this generation/injection easier, the `dns-proto.h`
+      file includes C++ helper classes for building DNS packets.
+ - Other library entrypoints that don't require network activity
+   (e.g. `ares_parse_*_reply`) are tested directly.
+ - A couple of the tests use a helper method of the test fixture to
+   inject memory allocation failures, using a recent change to the
+   c-ares library that allows override of `malloc`/`free`.
+ - There are some tests of the internal entrypoints of the library
+   (`ares-test-internal.c`), but these are only enabled if the library
+   was configured with `--disable-symbol-hiding` and/or
+   `--enable-expose-statics`.
+ - There is also an entrypoint to allow Clang's
+   [libfuzzer](http://llvm.org/docs/LibFuzzer.html) to drive
+   the packet parsing code in `ares_parse_*_reply`, together with a
+   standalone wrapper for it (`./aresfuzz`) to allow use of command
+   line fuzzers (such as [afl-fuzz](http://lcamtuf.coredump.cx/afl/))
+   for further fuzz testing.
+
+
+Code Coverage Information
+-------------------------
+
+To generate code coverage information:
+
+ - Configure both the library and the tests with `./configure
+   --enable-code-coverage` before building. This requires the relevant code
+   coverage tools ([gcov](https://gcc.gnu.org/onlinedocs/gcc/Gcov.html),
+   [lcov](http://ltp.sourceforge.net/coverage/lcov.php)) to be installed locally.
+ - Run the tests with `test/arestest`.
+ - Generate code coverage output with `make code-coverage-capture` in the
+   library directory (i.e. not in `test/`).