docs: revamp testing documentation (#2155)

# What does this PR do?
reduces duplication and centralizes information to be easier to find for
contributors

Signed-off-by: Nathan Weinberg <nweinber@redhat.com>

tests/README.md

@@ -0,0 +1,9 @@
+# Llama Stack Tests
+
+Llama Stack has multiple layers of testing done to ensure continuous functionality and prevent regressions to the codebase.
+
+| Testing Type | Details |
+|--------------|---------|
+| Unit | [unit/README.md](unit/README.md) |
+| Integration | [integration/README.md](integration/README.md) |
+| Verification | [verifications/README.md](verifications/README.md) |

tests/integration/README.md

@@ -11,7 +11,7 @@ pytest --help
 Here are the most important options:
 - `--stack-config`: specify the stack config to use. You have three ways to point to a stack:
   - a URL which points to a Llama Stack distribution server
-  - a template (e.g., `fireworks`, `together`) or a path to a run.yaml file
+  - a template (e.g., `fireworks`, `together`) or a path to a `run.yaml` file
   - a comma-separated list of api=provider pairs, e.g. `inference=fireworks,safety=llama-guard,agents=meta-reference`. This is most useful for testing a single API surface.
 - `--env`: set environment variables, e.g. --env KEY=value. this is a utility option to set environment variables required by various providers.
 

tests/unit/README.md

@@ -0,0 +1,21 @@
+# Llama Stack Unit Tests
+
+You can run the unit tests by running:
+
+```bash
+source .venv/bin/activate
+./scripts/unit-tests.sh [PYTEST_ARGS]
+```
+
+Any additional arguments are passed to pytest. For example, you can specify a test directory, a specific test file, or any pytest flags (e.g., -vvv for verbosity). If no test directory is specified, it defaults to "tests/unit", e.g:
+
+```bash
+./scripts/unit-tests.sh tests/unit/registry/test_registry.py -vvv
+```
+
+If you'd like to run for a non-default version of Python (currently 3.10), pass `PYTHON_VERSION` variable as follows:
+
+```
+source .venv/bin/activate
+PYTHON_VERSION=3.13 ./scripts/unit-tests.sh
+```

tests/verifications/README.md

@@ -4,7 +4,7 @@ Llama Stack Verifications provide standardized test suites to ensure API compati
 
 ## Overview
 
-This framework allows you to run the same set of verification tests against different LLM providers'  OpenAI-compatible endpoints (Fireworks, Together, Groq, Cerebras, etc., and OpenAI itself) to ensure they meet the expected behavior and interface standards.
+This framework allows you to run the same set of verification tests against different LLM providers' OpenAI-compatible endpoints (Fireworks, Together, Groq, Cerebras, etc., and OpenAI itself) to ensure they meet the expected behavior and interface standards.
 
 ## Features