Modify Software Tests page of the developer's guide to be requirement…

…s-agnostic (#5765)

A duplicate of
[#5740](#5740) due to doc
building issues.

Modify Software Tests page of the developer's guide to be
requirements-agnostic

**Context:**
Software Tests page was outdated and relied on listing the testing
requirements instead of relying on the continuously updated
`requirements-dev.txt` file.

**Description of the Change:**
Instructions for installing the development requirements was added to
the Installation page and the Requirements section of Software Tests has
been modified to be more informative rather than instructive.

**Benefits:**
Less overhead to update the guide later if deps are added/removed.

[[sc-63429](https://app.shortcut.com/xanaduai/story/63429)]

---------

Co-authored-by: Thomas R. Bromley <49409390+trbromley@users.noreply.github.com>

doc/development/guide/installation.rst

@@ -66,6 +66,14 @@ importing PennyLane in Python.
     requires ``pip install -e .`` to be re-run in the plugin repository
     for the changes to take effect.
 
+Apart from the core packages needed to run PennyLane. Some extra packages need
+to be installed for several development processes, such as linting, testing, and
+pre-commit quality checks. Those can be installed easily via ``pip``:
+
+.. code-block:: bash
+
+    pip install -r requirements-dev.txt
+
 Docker
 ------
 

doc/development/guide/tests.rst

@@ -3,17 +3,17 @@ Software tests
 
 Requirements
 ~~~~~~~~~~~~
-The PennyLane test suite requires the Python ``pytest`` package, as well as:
+The PennyLane test suite requires the Python ``pytest`` package, as well as
+some extentions thereof, for example:
 
 * ``pytest-cov``: determines test coverage
 * ``pytest-mock``: allows replacing components with dummy/mock objects
 * ``flaky``: manages tests with non-deterministic behaviour
+* ``pytest-benchmark``: benchmarks the performance of functions, and can be used to ensure consistent runtime
+* ``pytest-xdist``: currently used to force some tests to run on the same thread to avoid race conditions
 
-These requirements can be installed via ``pip``:
-
-.. code-block:: bash
-
-    pip install pytest pytest-cov pytest-mock flaky
+If you properly followed the :doc:`installation guide <./installation>`, you should have all of these packages and others installed in your
+environment, so you can go ahead and put your code to the test!
 
 Creating a test
 ~~~~~~~~~~~~~~~