Fix up bisect every which way

lib/mod_list_troubleshooter.dart

@@ -26,7 +26,10 @@ class ModListTroubleshooter {
 
   ModList binaryForward() {
     final midIndex = (_startIndex + _endIndex) ~/ 2;
-    final subset = originalModList.activeMods.keys.toList().sublist(midIndex);
+    final subset = originalModList.activeMods.keys.toList().sublist(
+      midIndex,
+      _endIndex,
+    );
     currentModList.disableAll();
     currentModList.enableMods(subset);
     _startIndex = midIndex;
@@ -36,7 +39,7 @@ class ModListTroubleshooter {
   ModList binaryBackward() {
     final midIndex = ((_startIndex + _endIndex) / 2).ceil();
     final subset = originalModList.activeMods.keys.toList().sublist(
-      0,
+      _startIndex,
       midIndex,
     );
     currentModList.disableAll();

test/mod_list_troubleshooter_test.dart

@@ -116,6 +116,29 @@ void main() {
         result = troubleshooter.binaryBackward();
         expect(result.activeMods.length, equals(2));
 
+        result = troubleshooter.binaryBackward();
+        expect(result.activeMods.length, equals(1));
+      },
+    );
+    test(
+      'Bisect search should end up with half the mods every iteration until 1',
+      () {
+        final troubleshooter = ModListTroubleshooter(modList);
+
+        var result = troubleshooter.binaryBackward();
+        // Half of our initial 30
+        expect(result.activeMods.length, equals(15));
+
+        result = troubleshooter.binaryForward();
+        // Half of our previous result
+        expect(result.activeMods.length, equals(8));
+
+        result = troubleshooter.binaryBackward();
+        expect(result.activeMods.length, equals(4));
+
+        result = troubleshooter.binaryForward();
+        expect(result.activeMods.length, equals(2));
+
         result = troubleshooter.binaryBackward();
         expect(result.activeMods.length, equals(1));
       },