server : replace behave with pytest (#10416)

* server : replace behave with pytest

* fix test on windows

* misc

* add more tests

* more tests

* styling

* log less, fix embd test

* added all sequential tests

* fix coding style

* fix save slot test

* add parallel completion test

* fix parallel test

* remove feature files

* update test docs

* no cache_prompt for some tests

* add test_cache_vs_nocache_prompt

examples/server/tests/unit/test_ctx_shift.py

@@ -0,0 +1,67 @@
+import pytest
+from utils import *
+
+server = ServerPreset.tinyllama2()
+
+
+LONG_TEXT = """
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
+Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
+""".strip()
+
+@pytest.fixture(scope="module", autouse=True)
+def create_server():
+    global server
+    server = ServerPreset.tinyllama2()
+    server.n_ctx = 256
+    server.n_slots = 2
+
+
+def test_ctx_shift_enabled():
+    # the prompt is 301 tokens
+    # the slot context is 256/2 = 128 tokens
+    # the prompt is truncated to keep the last 109 tokens
+    # 64 tokens are generated thanks to shifting the context when it gets full
+    global server
+    server.start()
+    res = server.make_request("POST", "/completion", data={
+        "n_predict": 64,
+        "prompt": LONG_TEXT,
+    })
+    assert res.status_code == 200
+    assert res.body["timings"]["prompt_n"] == 109
+    assert res.body["timings"]["predicted_n"] == 64
+    assert res.body["truncated"] is True
+
+
+@pytest.mark.parametrize("n_predict,n_token_output,truncated", [
+    (64, 64, False),
+    (-1, 120, True),
+])
+def test_ctx_shift_disabled_short_prompt(n_predict: int, n_token_output: int, truncated: bool):
+    global server
+    server.disable_ctx_shift = True
+    server.n_predict = -1
+    server.start()
+    res = server.make_request("POST", "/completion", data={
+        "n_predict": n_predict,
+        "prompt": "Hi how are you",
+    })
+    assert res.status_code == 200
+    assert res.body["timings"]["predicted_n"] == n_token_output
+    assert res.body["truncated"] == truncated
+
+
+def test_ctx_shift_disabled_long_prompt():
+    global server
+    server.disable_ctx_shift = True
+    server.start()
+    res = server.make_request("POST", "/completion", data={
+        "n_predict": 64,
+        "prompt": LONG_TEXT,
+    })
+    assert res.status_code != 200
+    assert "error" in res.body
+    assert "exceeds the available context size" in res.body["error"]["message"]