tests: Add -latest alias for each integration test suite (#5706)

## Summary
- For every auto-generated integration, adds a tox environment that
aliases the highest tested version (e.g. `tox -e py3.14-httpx-latest` =
`tox -e py3.14-httpx-v0.28.1`)
- Makes it easy to run tests against the latest version without looking
up exact version strings

## Notes
- The new latest env is NOT run in CI
- The new latest env points to the highest non-prerelease env

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: sentrivana

scripts/populate_tox/populate_tox.py

@@ -724,6 +724,31 @@ def _render_dependencies(integration: str, releases: list[Version]) -> list[str]
     return rendered
 
 
+def _render_latest_dependencies(
+    integration: str, latest_release: Version
+) -> list[str]:
+    """Render version-specific dependencies for the 'latest' alias.
+
+    Dependencies with "*" or "py3.*" constraints already match the latest
+    env via tox factor matching, so only version-specific constraints need
+    to be duplicated here.
+    """
+    rendered = []
+
+    if TEST_SUITE_CONFIG[integration].get("deps") is None:
+        return rendered
+
+    for constraint, deps in TEST_SUITE_CONFIG[integration]["deps"].items():
+        if constraint == "*" or constraint.startswith("py3"):
+            continue
+        restriction = SpecifierSet(constraint, prereleases=True)
+        if latest_release in restriction:
+            for dep in deps:
+                rendered.append(f"{integration}-latest: {dep}")
+
+    return rendered
+
+
 def write_tox_file(packages: dict) -> None:
     template = ENV.get_template("tox.jinja")
 
@@ -735,15 +760,30 @@ def write_tox_file(packages: dict) -> None:
     for group, integrations in packages.items():
         context["groups"][group] = []
         for integration in integrations:
+            # Find the highest stable (non-prerelease) release for the
+            # -latest alias.  Prereleases are always appended last by
+            # pick_releases_to_test, so we walk backwards.
+            latest_stable = None
+            for rel in reversed(integration["releases"]):
+                if not rel.is_prerelease:
+                    latest_stable = rel
+                    break
+
             context["groups"][group].append(
                 {
                     "name": integration["name"],
                     "package": integration["package"],
                     "extra": integration["extra"],
                     "releases": integration["releases"],
+                    "latest_stable": latest_stable,
                     "dependencies": _render_dependencies(
                         integration["name"], integration["releases"]
                     ),
+                    "latest_dependencies": _render_latest_dependencies(
+                        integration["name"], latest_stable
+                    )
+                    if latest_stable
+                    else [],
                 }
             )
             context["testpaths"].append(

scripts/populate_tox/tox.jinja

@@ -61,6 +61,9 @@ envlist =
     {% for release in integration.releases %}
     {{ release.rendered_python_versions }}-{{ integration.name }}-v{{ release }}
     {% endfor %}
+    {% if integration.latest_stable %}
+    {{ integration.latest_stable.rendered_python_versions }}-{{ integration.name }}-latest
+    {% endif %}
 
     {% endfor %}
 
@@ -143,9 +146,19 @@ deps =
     {{ integration.name }}-v{{ release }}: {{ integration.package }}=={{ release }}
     {% endif %}
     {% endfor %}
+    {% if integration.latest_stable %}
+    {% if integration.extra %}
+    {{ integration.name }}-latest: {{ integration.package }}[{{ integration.extra }}]=={{ integration.latest_stable }}
+    {% else %}
+    {{ integration.name }}-latest: {{ integration.package }}=={{ integration.latest_stable }}
+    {% endif %}
+    {% endif %}
     {% for dep in integration.dependencies %}
     {{ dep }}
     {% endfor %}
+    {% for dep in integration.latest_dependencies %}
+    {{ dep }}
+    {% endfor %}
 
     {% endfor %}
 

scripts/runtox.sh

@@ -15,7 +15,12 @@ fi
 
 searchstring="$1"
 
-ENV="$($TOXPATH -l | grep -- "$searchstring" | tr $'\n' ',')"
+# Filter out -latest environments unless explicitly requested
+if [[ "$searchstring" == *-latest* ]]; then
+    ENV="$($TOXPATH -l | grep -- "$searchstring" | tr $'\n' ',')"
+else
+    ENV="$($TOXPATH -l | grep -- "$searchstring" | grep -v -- '-latest$' | tr $'\n' ',')"
+fi
 
 if [ -z "${ENV}" ]; then
     echo "No targets found. Skipping."

scripts/split_tox_gh_actions/split_tox_gh_actions.py

@@ -240,6 +240,11 @@ def parse_tox():
             raw_python_versions = groups["py_versions"]
             framework = groups["framework"]
 
+            # The -latest env is an alias for the highest version of the
+            # same framework, so merge it with the base framework.
+            if framework.endswith("-latest"):
+                framework = framework[: -len("-latest")]
+
             # collect python versions to test the framework in
             raw_python_versions = set(raw_python_versions.split(","))
             py_versions[framework] |= raw_python_versions