Add tests to Atom

packages/dataverse/src/Atom.test.ts

@@ -0,0 +1,64 @@
+import {Atom} from '@theatre/dataverse'
+
+describe(`Atom`, () => {
+  test(`Usage of Atom and pointer, without prism`, async () => {
+    const data = {foo: 'foo', bar: 0}
+    const atom = new Atom(data)
+
+    // atom.get() returns an exact reference to the data
+    expect(atom.get()).toBe(data)
+
+    atom.set({foo: 'foo', bar: 1})
+
+    expect(atom.get()).not.toBe(data)
+    expect(atom.get()).toEqual({foo: 'foo', bar: 1})
+
+    atom.reduce(({foo, bar}) => ({foo, bar: bar + 1}))
+    expect(atom.get()).toEqual({foo: 'foo', bar: 2})
+
+    atom.setByPointer((p) => p.bar, 3)
+    expect(atom.get()).toEqual({foo: 'foo', bar: 3})
+
+    atom.setByPointer((p) => p.foo, 'foo2')
+    expect(atom.get()).toEqual({foo: 'foo2', bar: 3})
+
+    // this would work in runtime, but typescript will complain because `baz` is not a property of the state
+    // let's silence the error for the sake of the test
+    // @ts-ignore
+    atom.setByPointer((p) => p.baz, 'baz')
+    expect(atom.get()).toEqual({foo: 'foo2', bar: 3, baz: 'baz'})
+
+    atom.setByPointer((p) => p, {foo: 'newfoo', bar: -1})
+    expect(atom.get()).toEqual({foo: 'newfoo', bar: -1})
+
+    // `reduceByPointer()` is to `setByPointer()` what `reduce()` is to `set()`
+    atom.reduceByPointer(
+      (p) => p.bar,
+      (bar) => bar + 1,
+    )
+
+    expect(atom.get()).toEqual({foo: 'newfoo', bar: 0})
+
+    // we can use external pointers too
+    const externalPointer = atom.pointer.bar
+    atom.setByPointer(() => externalPointer, 1)
+    expect(atom.get()).toEqual({foo: 'newfoo', bar: 1})
+
+    let internalPointer
+    // the pointer passed to `setByPointer()` is the same as the one returned by `atom.pointer`
+    atom.setByPointer((p) => {
+      internalPointer = p
+      return p.bar
+    }, 2)
+
+    expect(internalPointer).toBe(atom.pointer)
+
+    expect(atom.pointer).toBe(atom.pointer)
+    expect(atom.pointer.bar).toBe(atom.pointer.bar)
+
+    // pointers don't change when the atom's state changes
+    const oldPointer = atom.pointer.bar
+    atom.set({foo: 'foo', bar: 10})
+    expect(atom.pointer.bar).toBe(oldPointer)
+  })
+})