doc: restructure developer docs to new layout

The developer oriented information is scattered in source
and its very difficult to identify which are those.
With this patch subdirs are created under developer-guide
which will be the parent for developer notes. The changes
suggested in http://review.gluster.org/#/c/8827/ are also
included in this patch.

Change-Id: I4c8510d52c49f4066225f72cac8f97f087d6c70c
BUG: 1206539
Signed-off-by: Humble Devassy Chirammal <hchiramm@redhat.com>
Reviewed-on: http://review.gluster.org/10038
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Lalatendu Mohanty <lmohanty@redhat.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>

1 files changed, 228 insertions, 0 deletions

diff --git a/doc/developer-guide/unittest.md b/doc/developer-guide/unittest.md
new file mode 100644
index 00000000000..5c6c0a8a039
--- /dev/null
+++ b/doc/developer-guide/unittest.md
@@ -0,0 +1,228 @@
+# Unit Tests in GlusterFS
+
+## Overview
+[Art-of-unittesting][definitionofunittest] provides a good definition for unit tests.  A good unit test is:
+
+* Able to be fully automated
+* Has full control over all the pieces running (Use mocks or stubs to achieve this isolation when needed)
+* Can be run in any order  if part of many other tests
+* Runs in memory (no DB or File access, for example)
+* Consistently returns the same result (You always run the same test, so no random numbers, for example. save those for integration or range tests)
+* Runs fast
+* Tests a single logical concept in the system
+* Readable
+* Maintainable
+* Trustworthy (when you see its result, you don’t need to debug the code just to be sure)
+
+## cmocka
+GlusterFS unit test framework is based on [cmocka][].  cmocka provides
+developers with methods to isolate and test modules written in C language.  It
+also provides integration with Jenkins by providing JUnit XML compliant unit
+test results.
+
+cmocka
+
+## Running Unit Tests
+To execute the unit tests, all you need is to type `make check`.  Here is a step-by-step example assuming you just cloned a GlusterFS tree:
+
+```
+$ ./autogen.sh
+$ ./configure --enable-debug
+$ make check
+```
+
+Sample output:
+
+```
+PASS: mem_pool_unittest
+============================================================================
+Testsuite summary for glusterfs 3git
+============================================================================
+# TOTAL: 1
+# PASS:  1
+# SKIP:  0
+# XFAIL: 0
+# FAIL:  0
+# XPASS: 0
+# ERROR: 0
+============================================================================
+```
+
+In this example, `mem_pool_unittest` has multiple tests inside, but `make check` assumes that the program itself is the test, and that is why it only shows one test.  Here is the output when we run `mem_pool_unittest` directly:
+
+```
+$ ./libglusterfs/src/mem_pool_unittest
+[==========] Running 10 test(s).
+[ RUN      ] test_gf_mem_acct_enable_set
+Expected assertion data != ((void *)0) occurred
+[       OK ] test_gf_mem_acct_enable_set
+[ RUN      ] test_gf_mem_set_acct_info_asserts
+Expected assertion xl != ((void *)0) occurred
+Expected assertion size > ((4 + sizeof (size_t) + sizeof (xlator_t *) + 4 + 8) + 8) occurred
+Expected assertion type <= xl->mem_acct.num_types occurred
+[       OK ] test_gf_mem_set_acct_info_asserts
+[ RUN      ] test_gf_mem_set_acct_info_memory
+[       OK ] test_gf_mem_set_acct_info_memory
+[ RUN      ] test_gf_calloc_default_calloc
+[       OK ] test_gf_calloc_default_calloc
+[ RUN      ] test_gf_calloc_mem_acct_enabled
+[       OK ] test_gf_calloc_mem_acct_enabled
+[ RUN      ] test_gf_malloc_default_malloc
+[       OK ] test_gf_malloc_default_malloc
+[ RUN      ] test_gf_malloc_mem_acct_enabled
+[       OK ] test_gf_malloc_mem_acct_enabled
+[ RUN      ] test_gf_realloc_default_realloc
+[       OK ] test_gf_realloc_default_realloc
+[ RUN      ] test_gf_realloc_mem_acct_enabled
+[       OK ] test_gf_realloc_mem_acct_enabled
+[ RUN      ] test_gf_realloc_ptr
+Expected assertion ((void *)0) != ptr occurred
+[       OK ] test_gf_realloc_ptr
+[==========] 10 test(s) run.
+[  PASSED  ] 10 test(s).
+[  FAILED  ] 0 test(s).
+[  REPORT  ] Created libglusterfs_mem_pool_xunit.xml report
+```
+
+
+## Writing Unit Tests
+
+### Enhancing your C functions
+
+#### Programming by Contract
+Add the following to your C file:
+
+```c
+#include <cmocka_pbc.h>
+```
+
+```c
+/*
+ * Programming by Contract is a programming methodology
+ * which binds the caller and the function called to a
+ * contract. The contract is represented using Hoare Triple:
+ *      {P} C {Q}
+ * where {P} is the precondition before executing command C,
+ * and {Q} is the postcondition.
+ *
+ * See also:
+ * http://en.wikipedia.org/wiki/Design_by_contract
+ * http://en.wikipedia.org/wiki/Hoare_logic
+ * http://dlang.org/dbc.html
+ */
+ #ifndef CMOCKERY_PBC_H_
+#define CMOCKERY_PBC_H_
+
+#if defined(UNIT_TESTING) || defined (DEBUG)
+
+#include <assert.h>
+
+/*
+ * Checks caller responsibility against contract
+ */
+#define REQUIRE(cond) assert(cond)
+
+/*
+ * Checks function reponsability against contract.
+ */
+#define ENSURE(cond) assert(cond)
+
+/*
+ * While REQUIRE and ENSURE apply to functions, INVARIANT
+ * applies to classes/structs.  It ensures that intances
+ * of the class/struct are consistent. In other words,
+ * that the instance has not been corrupted.
+ */
+#define INVARIANT(invariant_fnc) do{ (invariant_fnc) } while (0);
+
+#else
+#define REQUIRE(cond) do { } while (0);
+#define ENSURE(cond) do { } while (0);
+#define INVARIANT(invariant_fnc) do{ } while (0);
+
+#endif /* defined(UNIT_TESTING) || defined (DEBUG) */
+#endif /* CMOCKERY_PBC_H_ */
+```
+
+##### Example
+This is an _extremely_ simple example:
+
+```c
+int divide (int n, int d)
+{
+    int ans;
+
+    REQUIRE(d != 0);
+
+    ans = n / d;
+
+    // As code is added to this function throughout its lifetime,
+    // ENSURE will assert that data will be returned
+    // according to the contract.  Again this is an
+    // extremely simple example. :-D
+    ENSURE( ans == (n / d) );
+
+    return ans;
+}
+
+```
+
+##### Important Note
+`REQUIRE`, `ENSURE`, and `INVARIANT` are only available when `DEBUG` or `UNIT_TESTING` are set in the CFLAGS.  You must pass `--enable-debug` to `./configure` to enable PBC on your non-unittest builds.
+
+#### Overriding functions
+Cmockery2 provides its own memory allocation functions which check for buffer overrun and memory leaks.  The following header file must be included **last** to be able to override any of the memory allocation functions:
+
+```c
+#include <cmocka.h>
+```
+
+This file will only take effect with the `UNIT_TESTING` CFLAG is set.
+
+### Creating a unit test
+Once you identify the C file you would like to test, first create a `unittest` directory under the directory where the C file is located.  This will isolate the unittests to a different directory.
+
+Next, you need to edit the `Makefile.am` file in the directory where your C file is located.  Initialize the
+`Makefile.am` if it does not already have the following sections:
+
+```
+#### UNIT TESTS #####
+CLEANFILES += *.gcda *.gcno *_xunit.xml
+noinst_PROGRAMS =
+TESTS =
+```
+
+Now you can add the following for each of the unit tests that you would like to build:
+
+```
+### UNIT TEST xxx_unittest ###
+xxx_unittest_CPPFLAGS = $(xxx_CPPFLAGS)
+xxx_unittest_SOURCES = xxx.c \
+                       unittest/xxx_unittest.c
+xxx_unittest_CFLAGS = $(UNITTEST_CFLAGS)
+xxx_unittest_LDFLAGS = $(UNITTEST_LDFLAGS)
+noinst_PROGRAMS += xxx_unittest
+TESTS += xxx_unittest
+```
+
+Where `xxx` is the name of your C file. For example, look at `libglusterfs/src/Makefile.am`.
+
+Copy the simple unit test from the [cmocka API][cmockaapi] to `unittest/xxx_unittest.c`.  If you would like to see an example of a unit test, please refer to `libglusterfs/src/unittest/mem_pool_unittest.c`.
+
+#### Mocking
+You may see that the linker will complain about missing functions needed by the C file you would like to test.  Identify the required functions, then place their stubs in a file called `unittest/xxx_mock.c`, then include this file in `Makefile.am` in `xxx_unittest_SOURCES`.  This will allow you to you Cmockery2's mocking functions.
+
+#### Running the unit test
+You can type `make` in the directory where the C file is located.  Once you built it and there are no errors, you can execute the test either by directly executing the program (in our example above it is called `xxx_unittest` ), or by running `make check`.
+
+#### Debugging
+Sometimes you may need to debug your unit test.  To do that, you will have to point `gdb` to the binary which is located in the same directory as the source.  For example, you can do the following from the root of the source tree to debug `mem_pool_unittest`:
+
+```
+$ gdb libglusterfs/src/mem_pool_unittest
+```
+
+
+[cmocka]: https://cmocka.org
+[definitionofunittest]: http://artofunittesting.com/definition-of-a-unit-test/
+[cmockapi]: https://api.cmocka.org