docs/example-pytest-fixtures (#452)

Adds an example of test fixtures and `chdir`.

This option was quite hard to discover, however test fixtures are
common.

Co-authored-by: Alex Eagle <alex@aspect.dev>

Author: njlr

examples/pytest/BUILD.bazel

@@ -8,6 +8,7 @@ py_library(
 
 py_pytest_main(
     name = "__test__",
+    chdir = package_name(), # So that test fixtures are available at the correct path
     deps = [
         "@pypi_coverage//:pkg",
         "@pypi_pytest//:pkg",
@@ -24,6 +25,9 @@ py_test(
     imports = ["../.."],
     main = ":__test__.py",
     package_collisions = "warning",
+    data = glob([
+        "fixtures/*.json",
+    ]),
     deps = [
         ":__test__",
         ":lib",
@@ -43,6 +47,9 @@ py_test(
     imports = ["../.."],
     main = ":__test__.py",
     package_collisions = "warning",
+    data = glob([
+        "fixtures/*.json",
+    ]),
     deps = [
         ":__test__",
         ":lib",

examples/pytest/fixtures/hello.json

@@ -0,0 +1,3 @@
+{
+  "message": "Hello, world."
+}

examples/pytest/foo_test.py

@@ -1,6 +1,12 @@
 import pytest
+import json
 
 from examples.pytest.foo import add
 
 def test_add():
     assert add(1, 1) == 2, "Expected 1 + 1 to equal 2"
+
+def test_hello_json():
+    content = open('fixtures/hello.json', 'r').read()
+    data = json.loads(content)
+    assert data["message"] == "Hello, world.", "Message is as expected"