fix: address flaky tests (#3363)

fix: resolve flaky tests and race conditions in test suite

- Fix telemetry/event tests by patching class methods instead of instances
- Use unique temp files/directories to prevent CI race conditions
- Reset singleton state between tests
- Mock embedchain.Client.setup() to prevent JSON corruption
- Rename test files to test_*.py convention
- Move agent tests to tests/agents directory
- Fix repeated tool usage detection
- Remove database-dependent tools causing initialization errors

tests/cli/test_train_crew.py

@@ -0,0 +1,89 @@
+import subprocess
+from unittest import mock
+
+from crewai.cli.train_crew import train_crew
+
+
+@mock.patch("crewai.cli.train_crew.subprocess.run")
+def test_train_crew_positive_iterations(mock_subprocess_run):
+    n_iterations = 5
+    mock_subprocess_run.return_value = subprocess.CompletedProcess(
+        args=["uv", "run", "train", str(n_iterations)],
+        returncode=0,
+        stdout="Success",
+        stderr="",
+    )
+
+    train_crew(n_iterations, "trained_agents_data.pkl")
+
+    mock_subprocess_run.assert_called_once_with(
+        ["uv", "run", "train", str(n_iterations), "trained_agents_data.pkl"],
+        capture_output=False,
+        text=True,
+        check=True,
+    )
+
+
+@mock.patch("crewai.cli.train_crew.click")
+def test_train_crew_zero_iterations(click):
+    train_crew(0, "trained_agents_data.pkl")
+    click.echo.assert_called_once_with(
+        "An unexpected error occurred: The number of iterations must be a positive integer.",
+        err=True,
+    )
+
+
+@mock.patch("crewai.cli.train_crew.click")
+def test_train_crew_negative_iterations(click):
+    train_crew(-2, "trained_agents_data.pkl")
+    click.echo.assert_called_once_with(
+        "An unexpected error occurred: The number of iterations must be a positive integer.",
+        err=True,
+    )
+
+
+@mock.patch("crewai.cli.train_crew.click")
+@mock.patch("crewai.cli.train_crew.subprocess.run")
+def test_train_crew_called_process_error(mock_subprocess_run, click):
+    n_iterations = 5
+    mock_subprocess_run.side_effect = subprocess.CalledProcessError(
+        returncode=1,
+        cmd=["uv", "run", "train", str(n_iterations)],
+        output="Error",
+        stderr="Some error occurred",
+    )
+    train_crew(n_iterations, "trained_agents_data.pkl")
+
+    mock_subprocess_run.assert_called_once_with(
+        ["uv", "run", "train", str(n_iterations), "trained_agents_data.pkl"],
+        capture_output=False,
+        text=True,
+        check=True,
+    )
+    click.echo.assert_has_calls(
+        [
+            mock.call.echo(
+                "An error occurred while training the crew: Command '['uv', 'run', 'train', '5']' returned non-zero exit status 1.",
+                err=True,
+            ),
+            mock.call.echo("Error", err=True),
+        ]
+    )
+
+
+@mock.patch("crewai.cli.train_crew.click")
+@mock.patch("crewai.cli.train_crew.subprocess.run")
+def test_train_crew_unexpected_exception(mock_subprocess_run, click):
+    n_iterations = 5
+    mock_subprocess_run.side_effect = Exception("Unexpected error")
+    train_crew(n_iterations, "trained_agents_data.pkl")
+
+    mock_subprocess_run.assert_called_once_with(
+        ["uv", "run", "train", str(n_iterations), "trained_agents_data.pkl"],
+        capture_output=False,
+        text=True,
+        check=True,
+    )
+    click.echo.assert_called_once_with(
+        "An unexpected error occurred: Unexpected error", err=True
+    )