Feature: query-and-write find command

documentdb_tests/compatibility/tests/core/query_and_write/commands/find/test_find_combined.py

@@ -0,0 +1,66 @@
+"""Tests for find command with multiple options combined."""
+
+from __future__ import annotations
+
+import pytest
+
+from documentdb_tests.compatibility.tests.core.utils.command_test_case import (
+    CommandContext,
+    CommandTestCase,
+)
+from documentdb_tests.framework.assertions import assertResult
+from documentdb_tests.framework.executor import execute_command
+from documentdb_tests.framework.parametrize import pytest_params
+
+# Property [Combined Operations]: find correctly applies filter, sort, projection,
+# skip, limit, and let/$expr together in a single command.
+FIND_COMBINED_TESTS: list[CommandTestCase] = [
+    CommandTestCase(
+        "filter_sort_projection_skip_limit",
+        docs=[{"_id": i, "a": i % 3, "b": i * 10, "c": f"val_{i}"} for i in range(10)],
+        command=lambda ctx: {
+            "find": ctx.collection,
+            "filter": {"a": 0},
+            "sort": {"b": -1},
+            "projection": {"b": 1},
+            "skip": 1,
+            "limit": 2,
+        },
+        expected=[{"_id": 6, "b": 60}, {"_id": 3, "b": 30}],
+        msg="find should combine filter, sort, projection, skip, and limit correctly.",
+    ),
+    CommandTestCase(
+        "let_expr_sort_projection",
+        docs=[
+            {"_id": 1, "score": 80, "name": "Alice"},
+            {"_id": 2, "score": 95, "name": "Bob"},
+            {"_id": 3, "score": 70, "name": "Charlie"},
+        ],
+        command=lambda ctx: {
+            "find": ctx.collection,
+            "filter": {"$expr": {"$gte": ["$score", "$$threshold"]}},
+            "let": {"threshold": 80},
+            "sort": {"score": -1},
+            "projection": {"name": 1, "score": 1},
+        },
+        expected=[
+            {"_id": 2, "name": "Bob", "score": 95},
+            {"_id": 1, "name": "Alice", "score": 80},
+        ],
+        msg="find should combine let, $expr, sort, and projection.",
+    ),
+]
+
+
+@pytest.mark.parametrize("test", pytest_params(FIND_COMBINED_TESTS))
+def test_find_combined(database_client, collection, test):
+    """Test find command combined operations."""
+    collection = test.prepare(database_client, collection)
+    ctx = CommandContext.from_collection(collection)
+    result = execute_command(collection, test.build_command(ctx))
+    assertResult(
+        result,
+        expected=test.build_expected(ctx),
+        error_code=test.error_code,
+        msg=test.msg,
+    )

documentdb_tests/compatibility/tests/core/query_and_write/commands/find/test_find_core_behavior.py

@@ -0,0 +1,111 @@
+"""Tests for find command core behavior and response structure."""
+
+from __future__ import annotations
+
+import pytest
+from bson import Int64
+
+from documentdb_tests.compatibility.tests.core.utils.command_test_case import (
+    CommandContext,
+    CommandTestCase,
+)
+from documentdb_tests.framework.assertions import assertProperties, assertResult
+from documentdb_tests.framework.executor import execute_command
+from documentdb_tests.framework.parametrize import pytest_params
+from documentdb_tests.framework.property_checks import Eq, Exists, IsType
+
+# Property [Primary Operation]: find returns matching documents from a collection,
+# or all documents when no filter is specified.
+FIND_CORE_TESTS: list[CommandTestCase] = [
+    CommandTestCase(
+        "all_documents_no_filter",
+        docs=[{"_id": 1, "a": 10}, {"_id": 2, "a": 20}, {"_id": 3, "a": 30}],
+        command=lambda ctx: {"find": ctx.collection, "sort": {"_id": 1}},
+        expected=[{"_id": 1, "a": 10}, {"_id": 2, "a": 20}, {"_id": 3, "a": 30}],
+        msg="find should return all documents when no filter specified.",
+    ),
+    CommandTestCase(
+        "filter_returns_matching",
+        docs=[{"_id": 1, "a": 10}, {"_id": 2, "a": 20}, {"_id": 3, "a": 10}],
+        command=lambda ctx: {"find": ctx.collection, "filter": {"a": 10}, "sort": {"_id": 1}},
+        expected=[{"_id": 1, "a": 10}, {"_id": 3, "a": 10}],
+        msg="find should return only documents matching the filter.",
+    ),
+    CommandTestCase(
+        "empty_collection",
+        docs=[],
+        command=lambda ctx: {"find": ctx.collection},
+        expected=[],
+        msg="find should return empty result for empty collection.",
+    ),
+    CommandTestCase(
+        "nonexistent_collection",
+        docs=None,
+        command=lambda ctx: {"find": ctx.collection},
+        expected=[],
+        msg="find should return empty result for non-existent collection.",
+    ),
+    CommandTestCase(
+        "empty_filter_returns_all",
+        docs=[{"_id": 1, "x": "a"}, {"_id": 2, "x": "b"}],
+        command=lambda ctx: {"find": ctx.collection, "filter": {}, "sort": {"_id": 1}},
+        expected=[{"_id": 1, "x": "a"}, {"_id": 2, "x": "b"}],
+        msg="find should return all documents with empty filter.",
+    ),
+    CommandTestCase(
+        "multiple_conditions_implicit_and",
+        docs=[{"_id": 1, "a": 1, "b": 2}, {"_id": 2, "a": 1, "b": 3}],
+        command=lambda ctx: {"find": ctx.collection, "filter": {"a": 1, "b": 2}},
+        expected=[{"_id": 1, "a": 1, "b": 2}],
+        msg="find should use implicit AND for multiple filter conditions.",
+    ),
+    CommandTestCase(
+        "nested_field_dot_notation",
+        docs=[{"_id": 1, "obj": {"x": 10}}, {"_id": 2, "obj": {"x": 20}}],
+        command=lambda ctx: {"find": ctx.collection, "filter": {"obj.x": 10}},
+        expected=[{"_id": 1, "obj": {"x": 10}}],
+        msg="find should match nested fields using dot notation.",
+    ),
+]
+
+
+@pytest.mark.parametrize("test", pytest_params(FIND_CORE_TESTS))
+def test_find_core_behavior(database_client, collection, test):
+    """Test find command core behavior."""
+    collection = test.prepare(database_client, collection)
+    ctx = CommandContext.from_collection(collection)
+    result = execute_command(collection, test.build_command(ctx))
+    assertResult(
+        result,
+        expected=test.build_expected(ctx),
+        error_code=test.error_code,
+        msg=test.msg,
+    )
+
+
+def test_find_response_structure(collection):
+    """Test find response contains cursor with firstBatch, id, and ns fields."""
+    collection.insert_one({"_id": 1, "a": 1})
+    result = execute_command(collection, {"find": collection.name})
+    assertResult(
+        result,
+        expected={
+            "cursor.firstBatch": Exists(),
+            "cursor.id": IsType("long"),
+            "cursor.ns": IsType("string"),
+        },
+        raw_res=True,
+        msg="find should return cursor with firstBatch, id, and ns.",
+    )
+
+
+def test_find_cursor_id_zero_when_exhausted(collection):
+    """Test cursor id is 0 when all results fit in first batch."""
+    collection.insert_many([{"_id": i} for i in range(3)])
+    result = execute_command(collection, {"find": collection.name})
+    assertProperties(
+        result,
+        {"cursor.id": Eq(Int64(0))},
+        raw_res=True,
+        msg="find should return cursor id 0 when all results returned.",
+    )