diff --git a/docs/development.md b/docs/development.md
index 1c6bde5..75834f9 100644
--- a/docs/development.md
+++ b/docs/development.md
@@ -70,6 +70,19 @@ All module-internal names are prefixed with an underscore. Such names should
 not be used from another module. Modules must avoid reaching into each other's
 internals.
 
+## Testing
+
+Everything should have a unit test. In this project, we avoid access to the
+internet and to the user's cjdk cache directory in all unit tests. Instead,
+temporary directories are used to mock the cache, and, where needed, a mock
+server is used to test downloads.
+
+Unit test modules should try not to import cjdk modules other than the one
+under test, although sometimes this is unavoidable.
+
+Actual use of the internet (including the Coursier index) and the user cache
+directory is limited to integration tests, which are kept separate.
+
 (versioning-scheme)=
 
 ## Versioning
diff --git a/tests/test_api.py b/tests/test_api.py
index 10f4e91..c32d860 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -154,37 +154,3 @@ def test_env_var_set():
     with f("CJDK_TEST_ENV_VAR", "testvalue"):
         assert os.environ["CJDK_TEST_ENV_VAR"] == "testvalue"
     assert "CJDK_TEST_ENV_VAR" not in os.environ
-
-
-def test_list_vendors():
-    vendors = _api.list_vendors()
-    assert vendors is not None
-    assert "adoptium" in vendors
-    assert "corretto" in vendors
-    assert "graalvm" in vendors
-    assert "ibm-semeru-openj9" in vendors
-    assert "java-oracle" in vendors
-    assert "liberica" in vendors
-    assert "temurin" in vendors
-    assert "zulu" in vendors
-
-
-def test_list_jdks():
-    jdks = _api.list_jdks(cached_only=False)
-    assert jdks is not None
-    assert "adoptium:1.21.0.4" in jdks
-    assert "corretto:21.0.4.7.1" in jdks
-    assert "graalvm-community:21.0.2" in jdks
-    assert "graalvm-java21:21.0.2" in jdks
-    assert "liberica:22.0.2" in jdks
-    assert "temurin:1.21.0.4" in jdks
-    assert "zulu:8.0.362" in jdks
-
-    cached_jdks = _api.list_jdks()
-    assert cached_jdks is not None
-    assert len(cached_jdks) < len(jdks)
-
-    zulu_jdks = _api.list_jdks(vendor="zulu", cached_only=False)
-    assert zulu_jdks is not None
-    assert len(set(zulu_jdks))
-    assert all(jdk.startswith("zulu:") for jdk in zulu_jdks)
diff --git a/tests/test_integration.py b/tests/test_integration.py
new file mode 100644
index 0000000..ae21b19
--- /dev/null
+++ b/tests/test_integration.py
@@ -0,0 +1,39 @@
+# This file is part of cjdk.
+# Copyright 2022-25 Board of Regents of the University of Wisconsin System
+# SPDX-License-Identifier: MIT
+
+from cjdk import _api
+
+
+def test_list_vendors():
+    vendors = _api.list_vendors()
+    assert vendors is not None
+    assert "adoptium" in vendors
+    assert "corretto" in vendors
+    assert "graalvm" in vendors
+    assert "ibm-semeru-openj9" in vendors
+    assert "java-oracle" in vendors
+    assert "liberica" in vendors
+    assert "temurin" in vendors
+    assert "zulu" in vendors
+
+
+def test_list_jdks():
+    jdks = _api.list_jdks(cached_only=False)
+    assert jdks is not None
+    assert "adoptium:1.21.0.4" in jdks
+    assert "corretto:21.0.4.7.1" in jdks
+    assert "graalvm-community:21.0.2" in jdks
+    assert "graalvm-java21:21.0.2" in jdks
+    assert "liberica:22.0.2" in jdks
+    assert "temurin:1.21.0.4" in jdks
+    assert "zulu:8.0.362" in jdks
+
+    cached_jdks = _api.list_jdks()
+    assert cached_jdks is not None
+    assert len(cached_jdks) < len(jdks)
+
+    zulu_jdks = _api.list_jdks(vendor="zulu", cached_only=False)
+    assert zulu_jdks is not None
+    assert len(set(zulu_jdks))
+    assert all(jdk.startswith("zulu:") for jdk in zulu_jdks)