fix(fixtures/update): correct DBFit semantics — '=' suffix marks SET, bare marks WHERE

The previous implementation had the convention inverted. In DBFit, a header
written as 'colname=' reads as 'set this column to the cell value' (SET);
a bare 'colname' means 'find the row by matching this column' (WHERE).
Tests + docstring updated.

KBGSuite end-to-end against live Oracle: 6/6 pages green.

Author: Jürgen Zornig

src/dbression/fixtures/basic.py

@@ -231,8 +231,10 @@ class Update(Fixture):
 
     Convention (DBFit-compatible):
 
-    * Headers ending in ``=`` mark **WHERE columns** (the row's value is used in the WHERE clause).
-    * All other headers are **SET columns** (assigned to the new value).
+    * Headers ending in ``=`` mark **SET columns** (assigned to the new value — the ``=``
+      reads as "set this to whatever").
+    * All other headers are **WHERE columns** (the row's value is used in the WHERE
+      clause to locate the row).
 
     Data-cell substitution: ``<<sym`` reads from the symbol table, empty / ``null`` becomes NULL.
     Each data row issues one ``UPDATE`` statement. NULL on a WHERE column generates ``IS NULL``
@@ -241,10 +243,10 @@ class Update(Fixture):
     Example::
 
         !|Update|wlk.app_selectset|
-        |selected|oid=|table_name=|
-        |true    |42  |WB         |
+        |selected=|oid|table_name|
+        |true     |42 |WB        |
 
-    runs ``UPDATE wlk.app_selectset SET selected = :v_0 WHERE oid = :v_1 AND table_name = :v_2``.
+    runs ``UPDATE wlk.app_selectset SET selected = :s_0 WHERE oid = :w_1 AND table_name = :w_2``.
     """
 
     def run(self, table: Table, ctx: FixtureContext) -> FixtureResult:
@@ -260,13 +262,13 @@ def run(self, table: Table, ctx: FixtureContext) -> FixtureResult:
         for c_i, raw in enumerate(table.headers):
             h = raw.strip()
             if h.endswith("="):
-                where_columns.append((c_i, h[:-1].strip()))
+                set_columns.append((c_i, h[:-1].strip()))
             else:
-                set_columns.append((c_i, h))
+                where_columns.append((c_i, h))
         if not set_columns:
             return FixtureResult(
                 passed=False,
-                message="Update has no SET columns (every header ends with `=`)",
+                message="Update has no SET columns (no header ends with `=`)",
             )
 
         updated = 0

tests/test_update_fixture.py

@@ -1,4 +1,9 @@
-"""Update fixture tests against in-memory SQLite (no DB setup needed)."""
+"""Update fixture tests against in-memory SQLite (no DB setup needed).
+
+DBFit convention recap:
+  - Header ending in `=`  → SET column ("set this to whatever")
+  - Bare header           → WHERE column (lookup criterion)
+"""
 from __future__ import annotations
 
 import pytest
@@ -40,7 +45,7 @@ def test_update_set_one_column_where_id(conn) -> None:
     res, _ = _run_update(
         conn,
         args=["kunde"],
-        headers=["ort", "id="],
+        headers=["ort=", "id"],  # SET ort, WHERE id
         rows=[["Salzburg", "1"]],
     )
     assert res.passed, res.message
@@ -53,7 +58,7 @@ def test_update_multi_set_multi_where(conn) -> None:
     res, _ = _run_update(
         conn,
         args=["kunde"],
-        headers=["name", "ort", "id="],
+        headers=["name=", "ort=", "id"],
         rows=[["BobNeu", "Graz", "2"]],
     )
     assert res.passed
@@ -65,7 +70,7 @@ def test_update_multiple_rows_each_with_own_where(conn) -> None:
     res, _ = _run_update(
         conn,
         args=["kunde"],
-        headers=["ort", "id="],
+        headers=["ort=", "id"],
         rows=[["Graz", "1"], ["Innsbruck", "3"]],
     )
     assert res.passed
@@ -82,7 +87,7 @@ def test_update_with_symbol_substitution(conn) -> None:
     tbl = Table(
         name="Update",
         header_args=["kunde"],
-        headers=["ort", "id="],
+        headers=["ort=", "id"],
         rows=[["<<new_ort", "<<target_id"]],
     )
     res = cls().run(tbl, ctx)
@@ -97,7 +102,7 @@ def test_update_null_in_where_uses_is_null(conn) -> None:
     res, _ = _run_update(
         conn,
         args=["kunde"],
-        headers=["name", "ort="],
+        headers=["name=", "ort"],
         rows=[["Found", "null"]],
     )
     assert res.passed
@@ -109,14 +114,14 @@ def test_update_no_set_columns_fails_gracefully(conn) -> None:
     res, _ = _run_update(
         conn,
         args=["kunde"],
-        headers=["id=", "name="],
+        headers=["id", "name"],  # no `=` anywhere → no SET columns
         rows=[["1", "Anna"]],
     )
     assert not res.passed
     assert "no SET columns" in res.message
 
 
 def test_update_without_table_name_fails(conn) -> None:
-    res, _ = _run_update(conn, args=[], headers=["x"], rows=[["1"]])
+    res, _ = _run_update(conn, args=[], headers=["x="], rows=[["1"]])
     assert not res.passed
     assert "table name" in res.message