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src/test/java/puzzle/SwedishGeneratorTest.java

@@ -255,6 +255,49 @@ public class SwedishGeneratorTest {
       assertNotNull(g4);
    }
    
+   @Test
+   void testPlaceWord() {
+      var grid = SwedishGenerator.makeEmptyGrid();
+      // Slot at (0,0) length 3, horizontal (right)
+      // key = (r << 8) | (c << 4) | d. Here we just need a valid slot for placeWord.
+      // r(i) and c(i) are used by placeWord.
+      var packedPos = ((long) Grid.offset(0, 0)) | (((long) Grid.offset(0, 1)) << 7) | (((long) Grid.offset(0, 2)) << 14);
+      var s = Slot.from(0, packedPos, 3);
+      var w1 = new Lemma("ABC", 1, "test");
+      var undoBuffer = new long[10];
+      
+      // 1. Successful placement in empty grid
+      int placed = SwedishGenerator.placeWord(grid, s, w1, undoBuffer, 0);
+      assertEquals(3, placed);
+      assertEquals('A', grid.getCharAt(0, 0));
+      assertEquals('B', grid.getCharAt(0, 1));
+      assertEquals('C', grid.getCharAt(0, 2));
+      
+      // 2. Successful placement with partial overlap (same characters)
+      // Clear grid first or use another slot. Let's just verify it works if we place it again.
+      placed = SwedishGenerator.placeWord(grid, s, w1, undoBuffer, 0);
+      assertEquals(0, placed); // 0 new characters placed
+      
+      // 3. Conflict: place "ABD" where "ABC" is
+      var w2 = new Lemma("ABD", 1, "conflict");
+      placed = SwedishGenerator.placeWord(grid, s, w2, undoBuffer, 0);
+      assertEquals(-1, placed);
+      // Verify grid is unchanged (still "ABC")
+      assertEquals('A', grid.getCharAt(0, 0));
+      assertEquals('B', grid.getCharAt(0, 1));
+      assertEquals('C', grid.getCharAt(0, 2));
+      
+      // 4. Partial placement then conflict (rollback)
+      grid = SwedishGenerator.makeEmptyGrid();
+      grid.setCharAt(0, 2, 'X'); // Conflict at the end
+      placed = SwedishGenerator.placeWord(grid, s, w1, undoBuffer, 0);
+      assertEquals(-1, placed);
+      // Verify grid is still empty (except for 'X')
+      assertEquals(SwedishGenerator.C_DASH, grid.getCharAt(0, 0));
+      assertEquals(SwedishGenerator.C_DASH, grid.getCharAt(0, 1));
+      assertEquals('X', grid.getCharAt(0, 2));
+   }
+   
    @Test
    void testBacktrackingHelpers() {
       var grid = SwedishGenerator.makeEmptyGrid();