Update API tests README.md with current information (#5348)

Author: jhendersonHDF

test/API/README.md

@@ -5,8 +5,8 @@ public API and serve as regression tests for HDF5 [VOL Connectors](https://hdfgr
 
 ## Build Process and options
 
-These HDF5 API tests are disabled by default, but can be enabled by passing the
-`-DHDF5_TEST_API=ON` option to CMake. The following build options are available
+These HDF5 API tests are enabled by default, but can be disabled by passing the
+`-DHDF5_TEST_API=OFF` option to CMake. The following build options are available
 to influence how the API tests get built:
 
 ### CMake
@@ -18,7 +18,7 @@ For example,
 
 `HDF5_TEST_API` (Default: `ON`) - Determines whether the API tests will be built.
 
-`HDF5_TEST_API_INSTALL` (Default: `ON`) - Determines whether the API tests should be installed
+`HDF5_TEST_API_INSTALL` (Default: `OFF`) - Determines whether the API tests should be installed
 on the system.
 
 `HDF5_TEST_API_ENABLE_ASYNC` (Default: `OFF`) - Determines whether tests for HDF5's asynchronous
@@ -28,7 +28,8 @@ this functionality, so these tests are directed towards VOL connectors that do.
 `HDF5_TEST_ENABLE_DRIVER` (Default: `OFF`) - Determines whether the API test driver program should
 be built. This driver program is useful when a VOL connector relies upon a server executable
 (as well as possible additional executables) in order to function. The driver program can be
-supplied with a server executable and 
+supplied with a server executable and server/client arguments to use when running the API
+tests.
 
 `HDF5_TEST_API_SERVER` (Default: empty string) - If `HDF5_TEST_ENABLE_DRIVER` is set to `ON`, this
 option should be edited to point to the server executable that the driver program should attempt
@@ -44,16 +45,19 @@ These API tests currently only support usage with the native HDF5 VOL connector
 connectors that can be loaded dynamically as a plugin. For information on how to build a VOL
 connector in this manner, refer to section 2.3 of the [HDF5 VOL Connector Author Guide](https://hdfgroup.github.io/hdf5/develop/_v_o_l__connector.html).
 
-TODO: section on building VOL connectors alongside HDF5 for use with tests
+If an HDF5 VOL connector has been built alongside the library, these API tests can be used
+for testing that VOL connector at the same time that HDF5 is test. For more information on
+how to build a VOL connector alongside the HDF5 library, refer to
+[Building and testing HDF5 VOL connectors with CMake FetchContent](https://hdfgroup.github.io/hdf5/develop/df/d6b/_c_make_vols.html).
 
 These API tests can also be used to test an HDF5 VOL connector that is external to the library.
 For convenience, the `HDF5_TEST_API_INSTALL` option can be used to install these tests on the
-system where other HDF5 executables (such as `h5dump`) are installed.
-
-To run these tests with your VOL connector, set the following two environment variables:
+system where other HDF5 executables (such as `h5dump`) are installed. To run these tests manually
+with your VOL connector, set the following two environment variables:
 
 `HDF5_VOL_CONNECTOR` - This environment variable should be set to the name chosen for the VOL connector
-to be used. For example, HDF5's DAOS VOL connector uses the name "[daos](https://github.com/HDFGroup/vol-daos/blob/v1.2.0/src/daos_vol.h#L30)" and would therefore set:
+to be used. For example, HDF5's DAOS VOL connector uses the name "[daos](https://github.com/HDFGroup/vol-daos/blob/v1.2.0/src/daos_vol.h#L30)"
+and would therefore set:
 
     HDF5_VOL_CONNECTOR=daos