# HG changeset patch
# User Mike Becker <universe@uap-core.de>
# Date 1788792649 -7200
# Node ID 338795f5837b8f240e86754ad492053fb98629c9
# Parent  04da225a5677ffb3f75b4e1c546e3dc432437446
fixes parsing of en-passant threat in fen_parse()

relates to #939

diff -r 04da225a5677 -r 338795f5837b src/chess/fen.c
--- a/src/chess/fen.c	Sat Sep 05 13:03:09 2026 +0200
+++ b/src/chess/fen.c	Mon Sep 07 16:50:49 2026 +0200
@@ -265,6 +265,7 @@
             }
             /* the threat is applied to the pawn, not the field it passed */
             enpassant_threat_add(gamestate, f, r);
+            str += 2;
         } else {
             return 1;
         }
diff -r 04da225a5677 -r 338795f5837b test/test-fen.c
--- a/test/test-fen.c	Sat Sep 05 13:03:09 2026 +0200
+++ b/test/test-fen.c	Mon Sep 07 16:50:49 2026 +0200
@@ -191,6 +191,32 @@
     gamestate_cleanup(&gs);
 }
 
+static CX_TEST(test_fen_enpassant) {
+    /* this test contains a full game where white is checkmated */
+    const char * fen = "rnQ4r/pp4kp/3p2pn/1BpPp1N1/5P2/2BK4/P1P3qP/8 w - e6 0 19";
+    GameState gs;
+    int result = fen_parse(fen, &gs);
+    CX_TEST_DO {
+        CX_TEST_ASSERT(result == 0);
+        /* verify that only e5 has an active enpassant threat */
+        for (File f = 0 ; f < 8 ; f++) {
+            for (Rank r = 0 ; r < 8 ; r++) {
+                if (f == fileidx('e') && r == rankidx('5')) {
+                    CX_TEST_ASSERT(enpassant_threat_exists(&gs, f, r));
+                } else {
+                    CX_TEST_ASSERT(!enpassant_threat_exists(&gs, f, r));
+                }
+            }
+        }
+
+        /* check that we get the original FEN back */
+        char fen_chk[FEN_MAX_LENGTH];
+        fen_compute(fen_chk, &gs);
+        CX_TEST_ASSERTM(strcmp(fen, fen_chk) == 0, fen_chk);
+    }
+    gamestate_cleanup(&gs);
+}
+
 CxTestSuite* test_fen_suite(void) {
     CxTestSuite* suite = cx_test_suite_new("Test FEN API");
 
@@ -198,7 +224,7 @@
     cx_test_register(suite, test_fen_with_castling_rights);
     cx_test_register(suite, test_fen_checkmate);
     // TODO: test FENs that describe stalemate, threefold, no-material positions
-    // TODO: test FEN with en-passant threat
+    cx_test_register(suite, test_fen_enpassant);
 
     return suite;
 }