LibTest+Spreadsheet: Add some basic spreadsheet runtime behaviour tests

As there's a somewhat active development going on, let's keep the
expected behaviour under tests to make sure nothing blows up :^)

Userland/Applications/Spreadsheet/Tests/basic.js

@@ -0,0 +1,97 @@
+describe("Position", () => {
+    test("here", () => {
+        const workbook = createWorkbook();
+        const sheet = createSheet(workbook, "Sheet 1");
+        sheet.makeCurrent();
+
+        sheet.setCell("A", 0, "0");
+        sheet.focusCell("A", 0);
+
+        expect(here).toBeDefined();
+        let position = here();
+        expect(position).toBeDefined();
+
+        expect(position.column).toEqual("A");
+        expect(position.name).toEqual("A0");
+        expect(position.row).toEqual(0);
+        expect(position.sheet).toBe(sheet);
+
+        expect(position.contents).toEqual("0");
+        expect(position.value()).toEqual("0");
+        expect(position.toString()).toEqual("<Cell at A0>");
+
+        position.contents = "=1 + 1";
+        expect(position.contents).toEqual("=1 + 1");
+        expect(position.value()).toEqual(2);
+
+        expect(position.up().row).toEqual(0);
+        expect(position.down().row).toEqual(1);
+        expect(position.right().row).toEqual(0);
+        expect(position.left().row).toEqual(0);
+
+        sheet.addColumn("B");
+        expect(position.up().column).toEqual("A");
+        expect(position.down().column).toEqual("A");
+        expect(position.right().column).toEqual("B");
+        expect(position.left().column).toEqual("A");
+    });
+
+    test("Position.from_name", () => {
+        const workbook = createWorkbook();
+        const sheet = createSheet(workbook, "Sheet 1");
+        sheet.makeCurrent();
+
+        sheet.setCell("A", 0, "0");
+        sheet.focusCell("A", 0);
+
+        expect(Position.from_name).toBeDefined();
+        let position = Position.from_name("A0");
+        expect(position).toBeInstanceOf(Position);
+
+        position = Position.from_name("A123");
+        expect(position).toBeInstanceOf(Position);
+    });
+});
+
+describe("Range", () => {
+    test("simple", () => {
+        const workbook = createWorkbook();
+        const sheet = createSheet(workbook, "Sheet 1");
+        sheet.makeCurrent();
+
+        sheet.setCell("A", 0, "0");
+        sheet.setCell("A", 10, "0");
+        sheet.setCell("B", 1, "0");
+        sheet.focusCell("A", 0);
+
+        expect(R).toBeDefined();
+        let cellsVisited = 0;
+        R`A0:A10`.forEach(name => {
+            ++cellsVisited;
+        });
+        expect(cellsVisited).toEqual(11);
+
+        cellsVisited = 0;
+        R`A0:A10:1:2`.forEach(name => {
+            ++cellsVisited;
+        });
+        expect(cellsVisited).toEqual(6);
+    });
+
+    test("Ranges", () => {
+        const workbook = createWorkbook();
+        const sheet = createSheet(workbook, "Sheet 1");
+        sheet.makeCurrent();
+
+        sheet.setCell("A", 0, "0");
+        sheet.setCell("A", 10, "0");
+        sheet.setCell("B", 1, "0");
+        sheet.focusCell("A", 0);
+
+        let cellsVisited = 0;
+        R`A0:A5`.union(R`A6:A10`).forEach(name => {
+            ++cellsVisited;
+        });
+        expect(cellsVisited).toEqual(11);
+    });
+});