Start writing python-integration test that starts simulation server

integration-tests/testfile.py

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+#! /usr/bin/env python3
+"""This module fires up a server in a subprocess to allow for integration tests.""
+
+These are seperated from the unit tests to stop them artificially inflating the test
+coverage. For now this file should be run directly not with a test framework
+"""
+
+import subprocess
+import os
+import shutil
+from time import sleep
+
+
+THIS_DIR = os.path.dirname(os.path.realpath(__file__))
+WORKING_DIR = os.path.join(THIS_DIR, "working_dir")
+REPO_DIR = os.path.dirname(THIS_DIR)
+CONFIG_FILE = os.path.join(REPO_DIR, "ofm_config_simulation.json")
+CMD = ["openflexure-microscope-server", "--fallback", "-c", CONFIG_FILE]
+
+
+def main():
+    """Set up the server, run basic checks, shutdown, check for graceful exit"""
+    set_up_working_dir()
+    os.chdir(WORKING_DIR)
+
+    try:
+        print("Starting server")
+        server_process = start_server()
+        print("Waiting 15s to ensure started up")
+        sleep(15)
+        error_if_server_not_started(server_process)
+
+    finally:
+        # Ensure the server process is really dead
+        if server_process.poll() is None:
+            print("Server still running, shutting down.")
+            server_process.terminate()
+            sleep(2)
+            if server_process.poll() is None:
+                server_process.kill()
+                raise RuntimeError("Server needed killing at end of test.")
+
+
+def set_up_working_dir() -> None:
+    """If working dir exists, delete it and make a new one."""
+    if os.path.exists(WORKING_DIR):
+        shutil.rmtree(WORKING_DIR)
+    os.makedirs(WORKING_DIR)
+
+
+def start_server() -> subprocess.Popen:
+    """
+    Start the server in a subprocess.
+
+    The server is started in a background thread and all outputs are
+    buffered.
+
+    :return: Popen object for the ongoing process
+    """
+    process = subprocess.Popen(
+        CMD,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+        bufsize=1,
+        universal_newlines=True,
+    )
+    os.set_blocking(process.stdout.fileno(), False)
+    os.set_blocking(process.stderr.fileno(), False)
+    return process
+
+
+def error_if_server_not_started(server_process: subprocess.Popen) -> None:
+    """Check the server started up as expected.
+
+    Check the subprocess is running
+    Check the logs have no errors
+    Read the Logs to check uvicorn is running on http://127.0.0.1:5000
+    """
+
+    stdout, stderr = read_process_buffers(server_process)
+    output = format_stdout_stderr(stdout, stderr)
+    if server_process.poll() is not None:
+        raise RuntimeError(f"Server process is not running!\n{output}")
+
+    confirmed_uvicorn_is_running = False
+    # Note that logs go to stderr once OFM logging process stars, but if there is an
+    # error very early (such as on import) on logs may go to stdout
+    for line in stdout + stderr:
+        if line.startswith("ERROR:"):
+            raise RuntimeError(f"Server started up with error\n{line}\n\n{output}")
+        if "Uvicorn running on http://127.0.0.1:5000" in line:
+            confirmed_uvicorn_is_running = True
+
+    if not confirmed_uvicorn_is_running:
+        raise RuntimeError(
+            f"Cannot confirm Uvicorn is running on http://127.0.0.1:5000\n\n{output}"
+        )
+
+    # If we reached here Everything is fine! print the logs!
+    print("Server is running with following outputs:\n\n")
+    print(output)
+
+
+def read_process_buffers(process: subprocess.Popen) -> tuple[list[str], list[str]]:
+    """Return STDOUT and STDERR from a process"""
+    stdout = []
+    stderr = []
+
+    while line := process.stdout.readline():
+        stdout.append(line)
+
+    while line := process.stderr.readline():
+        stderr.append(line)
+
+    return stdout, stderr
+
+
+def format_stdout_stderr(stdout: list[str], stderr: list[str]) -> str:
+    """Return a ready to print format for stdout and stderr"""
+    text = ""
+    if stdout:
+        text += "**STDOUT**\n" + "".join(stdout) + "\n"
+    else:
+        text += "**STDOUT IS EMPTY**\n\n"
+
+    if stderr:
+        text += "**STDERR**\n" + "".join(stderr) + "\n"
+    else:
+        text += "**STDERR IS EMPTY**\n\n"
+    return text
+
+
+if __name__ == "__main__":
+    main()