test(model): add workbook, dependency and json tests

test/dependency_test.dart

@@ -0,0 +1,93 @@
+import 'package:cellar/cellar.dart';
+import 'package:test/test.dart';
+
+double numberOf(CellValue value) => (value as NumberValue).value;
+
+void main() {
+  group('dependency graph recalculation', () {
+    test('changing a precedent recomputes a dependent', () {
+      final sheet = Sheet();
+      sheet.setValue('A1', '5');
+      sheet.setValue('B1', '=A1+1');
+      expect(numberOf(sheet.valueOf('B1')), 6);
+
+      sheet.setValue('A1', '10');
+      expect(numberOf(sheet.valueOf('B1')), 11);
+    });
+
+    test('a chain propagates through several levels', () {
+      final sheet = Sheet();
+      sheet.setValue('A1', '2');
+      sheet.setValue('B1', '=A1*2');
+      sheet.setValue('C1', '=B1*2');
+      sheet.setValue('D1', '=C1+1');
+      expect(numberOf(sheet.valueOf('D1')), 9);
+
+      sheet.setValue('A1', '5');
+      expect(numberOf(sheet.valueOf('B1')), 10);
+      expect(numberOf(sheet.valueOf('C1')), 20);
+      expect(numberOf(sheet.valueOf('D1')), 21);
+    });
+
+    test('a single precedent feeds multiple dependents', () {
+      final sheet = Sheet();
+      sheet.setValue('A1', '3');
+      sheet.setValue('B1', '=A1+1');
+      sheet.setValue('B2', '=A1*10');
+      sheet.setValue('B3', '=A1-1');
+      sheet.setValue('A1', '7');
+      expect(numberOf(sheet.valueOf('B1')), 8);
+      expect(numberOf(sheet.valueOf('B2')), 70);
+      expect(numberOf(sheet.valueOf('B3')), 6);
+    });
+
+    test('range dependencies recompute when a member changes', () {
+      final sheet = Sheet();
+      sheet.setValue('A1', '1');
+      sheet.setValue('A2', '2');
+      sheet.setValue('A3', '3');
+      sheet.setValue('B1', '=SUM(A1:A3)');
+      expect(numberOf(sheet.valueOf('B1')), 6);
+
+      sheet.setValue('A2', '20');
+      expect(numberOf(sheet.valueOf('B1')), 24);
+    });
+  });
+
+  group('cycle detection', () {
+    test('two cells referencing each other become #CYCLE!', () {
+      final sheet = Sheet();
+      sheet.setValue('A1', '=B1');
+      sheet.setValue('B1', '=A1');
+      expect(sheet.valueOf('A1'), const ErrorValue(ErrorKind.cycle));
+      expect(sheet.valueOf('B1'), const ErrorValue(ErrorKind.cycle));
+    });
+
+    test('self reference is a cycle', () {
+      final sheet = Sheet();
+      sheet.setValue('A1', '=A1+1');
+      expect(sheet.valueOf('A1'), const ErrorValue(ErrorKind.cycle));
+    });
+
+    test('a three cell cycle is detected', () {
+      final sheet = Sheet();
+      sheet.setValue('A1', '=B1');
+      sheet.setValue('B1', '=C1');
+      sheet.setValue('C1', '=A1');
+      expect(sheet.valueOf('A1'), const ErrorValue(ErrorKind.cycle));
+      expect(sheet.valueOf('B1'), const ErrorValue(ErrorKind.cycle));
+      expect(sheet.valueOf('C1'), const ErrorValue(ErrorKind.cycle));
+    });
+
+    test('breaking a cycle restores computation', () {
+      final sheet = Sheet();
+      sheet.setValue('A1', '=B1');
+      sheet.setValue('B1', '=A1');
+      expect(sheet.valueOf('A1'), const ErrorValue(ErrorKind.cycle));
+
+      sheet.setValue('B1', '5');
+      expect(numberOf(sheet.valueOf('B1')), 5);
+      expect(numberOf(sheet.valueOf('A1')), 5);
+    });
+  });
+}