test: add type testing (atomiks#743)

* test: add type testing

* chore: fix CI

* chore: run types tests before any other

.travis.yml

@@ -16,7 +16,7 @@ jobs:
 
     - stage: Code check
       name: Type checking
-      script: npm run check-types
+      script: npm run test:types
 
     - stage: Tests
       name: DOM tests

index.test-d.ts

@@ -0,0 +1,58 @@
+import {expectType} from 'tsd';
+import tippy, {
+  Instance,
+  delegate,
+  DelegateInstance,
+  createSingleton,
+  Plugin,
+  animateFill,
+  followCursor,
+  inlinePositioning,
+  sticky,
+  hideAll,
+  roundArrow,
+} from '.';
+
+const singleTarget = document.createElement('div');
+const mulitpleTargets = document.querySelectorAll('div');
+
+expectType<Instance>(tippy(singleTarget));
+expectType<Instance>(tippy(singleTarget, {content: 'hello'}));
+
+expectType<Instance[]>(tippy(mulitpleTargets));
+expectType<Instance[]>(tippy(mulitpleTargets, {content: 'hello'}));
+
+expectType<DelegateInstance>(delegate(singleTarget, {target: '.child'}));
+expectType<DelegateInstance>(
+  delegate(singleTarget, {target: '.child', content: 'hello'})
+);
+
+expectType<DelegateInstance[]>(delegate(mulitpleTargets, {target: '.child'}));
+expectType<DelegateInstance[]>(
+  delegate(mulitpleTargets, {target: '.child', content: 'hello'})
+);
+
+const tippyInstances = [tippy(singleTarget), tippy(singleTarget)];
+expectType<Instance>(createSingleton(tippyInstances));
+expectType<Instance>(createSingleton(tippyInstances, {content: 'hello'}));
+expectType<Instance>(createSingleton(tippyInstances, {overrides: ['content']}));
+
+expectType<Instance>(
+  tippy(singleTarget, {
+    plugins: [animateFill, followCursor, inlinePositioning, sticky],
+  })
+);
+
+const customPlugin: Plugin = {
+  name: 'custom',
+  defaultValue: 42,
+  fn(instance) {
+    expectType<Instance>(instance);
+    return {};
+  },
+};
+expectType<Instance>(tippy(singleTarget, {plugins: [customPlugin]}));
+
+expectType<void>(hideAll({duration: 50, exclude: tippy(singleTarget)}));
+
+expectType<string>(roundArrow);