Add type tests

Author: mAAdhaTTah

kefir-test-utils.test-d.ts

@@ -0,0 +1,24 @@
+import {expectType} from 'tsd'
+import Kefir from 'kefir'
+import {Clock} from 'lolex'
+import createHelpers, {Event, Watcher} from '.'
+
+const {VALUE, ERROR, END, value, error, end, withFakeTime, logItem, watch, watchWithTime} = createHelpers(Kefir)
+
+expectType<string>(VALUE)
+expectType<string>(ERROR)
+expectType<string>(END)
+
+expectType<Event<string, any>>(value('hello'))
+expectType<Event<any, string>>(error('hello'))
+expectType<Event<any, any>>(end())
+
+expectType<void>(
+  withFakeTime((tick: (s: number) => void, clock: Clock) => {
+    tick(10)
+    clock.runToLast()
+  })
+)
+expectType<Event<string, number>>(logItem({type: 'value', value: 'hello'}, false))
+expectType<Watcher<string, number>>(watch(new Kefir.Stream<string, number>()))
+expectType<Event<string, number>[]>(watchWithTime(new Kefir.Stream<string, number>()))