Add docs for running integration tests locally.

Fixes #141

PiperOrigin-RevId: 607109376

Author: Xee authors

README.md

@@ -92,6 +92,16 @@ ds = xarray.open_dataset(i, engine='ee')
 
 See [examples](https://github.com/google/Xee/tree/main/examples) or [docs](https://github.com/google/Xee/tree/main/docs) for more uses and integrations.
 
+## How to run integration tests
+
+The Xee integration tests only pass on Xee branches (no forks). Please run the
+integration tests locally before sending a PR. To run the tests locally,
+authenticate using `earthengine authenticate` and run the following:
+
+```bash
+USE_ADC_CREDENTIALS=1 python -m unittest xee/ext_integration_test.py
+```
+
 ## License
 
 This is not an official Google product.

xee/ext_integration_test.py

@@ -39,6 +39,7 @@
     'https://www.googleapis.com/auth/cloud-platform',
     'https://www.googleapis.com/auth/earthengine',
 ]
+_USE_ADC_CREDENTIALS_KEY = 'USE_ADC_CREDENTIALS'
 
 
 def _read_identity_pool_creds() -> identity_pool.Credentials:
@@ -50,10 +51,12 @@ def _read_identity_pool_creds() -> identity_pool.Credentials:
 
 
 def init_ee_for_tests():
-  ee.Initialize(
-      credentials=_read_identity_pool_creds(),
-      opt_url=ee.data.HIGH_VOLUME_API_BASE_URL,
-  )
+  init_params = {
+      'opt_url': ee.data.HIGH_VOLUME_API_BASE_URL,
+  }
+  if not os.environ.get(_USE_ADC_CREDENTIALS_KEY, False):
+    init_params['credentials'] = _read_identity_pool_creds()
+  ee.Initialize(**init_params)
 
 
 class EEBackendArrayTest(absltest.TestCase):