diff --git a/tests/test_api.py b/tests/test_api.py
index f4e62b9f..cba171a3 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -1,5 +1,7 @@
 import os
 
+import pytest
+
 import audeer
 import audformat
 
@@ -57,27 +59,92 @@ def test_available_broken_dataset(private_and_public_repository):
     assert "broken-dataset" not in df
 
 
-def test_available_repositories(tmpdir):
-    """Test repositories argument of available()."""
+class TestAvailable:
+    r"""Test collecting available datasets."""
+
     repositories = []
-    for n in range(2):
-        host = audeer.mkdir(tmpdir, f"host{n}")
-        repo = f"repo{n}"
-        repositories.append(audb.Repository(repo, host, "file-system"))
-        # Fake dataset by adding db.yaml file
-        audeer.touch(audeer.mkdir(host, repo, f"name{n}", "1.0.0"), "db.yaml")
-    # Look at all repositories
-    for repositories_argument in [None, repositories]:
-        df = audb.available(repositories=repositories_argument)
+    """Repositories."""
+
+    @classmethod
+    @pytest.fixture(scope="class", autouse=True)
+    def setup(cls, tmpdir_factory):
+        r"""Create two repositories containing a single dataset.
+
+        Args:
+            request: request fixture to access params
+            tmpdir_factory: tmpdir_factory fixture
+
+        """
+        current_repositories = audb.config.REPOSITORIES
+
+        for n in range(2):
+            host = str(tmpdir_factory.mktemp(f"host{n}"))
+            repo = f"repo{n}"
+            audeer.touch(audeer.mkdir(host, repo, f"name{n}", "1.0.0"), "db.yaml")
+            cls.repositories.append(audb.Repository(repo, host, "file-system"))
+
+        audb.config.REPOSITORIES = cls.repositories
+
+        yield
+
+        audb.config.REPOSITORIES = current_repositories
+
+    @pytest.fixture(scope="class", autouse=False)
+    def repository_with_empty_folder(self, tmpdir_factory):
+        """Create repository with empty folder.
+
+        An empty folder in a repository
+        should not be detected as a database.
+
+        """
+        repository = self.repositories[0]
+        empty_folder = audeer.mkdir(repository.host, repository.name, "no-database")
+        yield
+        audeer.rmdir(empty_folder)
+
+    def test_non_existing_database(self, repository_with_empty_folder):
+        """Test having a database only given as a folder."""
+        df = audb.available()
         assert len(df) == 2
-    for n, repository in enumerate(repositories):
-        # Test for string and list arguments
-        for repositories_argument in [repository, [repository]]:
-            df = audb.available(repositories=repositories_argument)
-            assert len(df) == 1
-            assert df.host.iloc[0] == repository.host
-            assert df.repository.iloc[0] == repository.name
-            assert df.index[0] == f"name{n}"
+        assert "no-database" not in df
+
+    def test_repositories_none(self):
+        """Test default value of repositories argument."""
+        print(f"{audb.config.REPOSITORIES=}")
+        df = audb.available(repositories=None)
+        print(df)
+        assert len(df) == 2
+
+    def test_repositories_all(self):
+        """Provide all repositories."""
+        df = audb.available(repositories=self.repositories)
+        assert len(df) == 2
+
+    @pytest.mark.parametrize("repository_index", [0, 1])
+    @pytest.mark.parametrize("as_list", [False, True])
+    def test_repositories_single(self, repository_index, as_list):
+        """Test looking to single repositories."""
+        repository = self.repositories[repository_index]
+        if as_list:
+            repositories = [repository]
+        else:
+            repositories = repository
+        df = audb.available(repositories=repositories)
+        assert len(df) == 1
+        assert df.host.iloc[0] == repository.host
+        assert df.repository.iloc[0] == repository.name
+        assert df.index[0] == f"name{repository_index}"
+
+    def test_repositories_non_existing_path(self):
+        """Test with non-existent path."""
+        invalid_repo = audb.Repository("invalid", "/nonexistent/path", "file-system")
+        df = audb.available(repositories=invalid_repo)
+        assert len(df) == 0
+
+    def test_repositories_malformed_repository(self):
+        """Test with malformed repository (string instead of Repository object)."""
+        with pytest.raises(AttributeError):
+            audb.available(repositories=["not-a-repository-object"])
 
 
 def test_versions(tmpdir, repository):