feat: migrate unit tests to Jest (#6353)

* config(jest): updated setup
* config(jest): update testMatch to include jsx files
* config(jest): add transformIgnorePatterns
* config(jest): update ignore files that do not work in jest yet
* config: add test:unit-jest to test script

* fix(jest): lint with eslint-plugin-jest

* refactor(jest): move unit test directory
* refactor(mocha): restore mocha tests that fail in jest

* docs(jest): update helpful scripts with test:unit-jest

test/unit/components/schemes.jsx

@@ -0,0 +1,69 @@
+import React from "react"
+import { shallow } from "enzyme"
+import { fromJS } from "immutable"
+import Schemes from "components/schemes"
+
+describe("<Schemes/>", function(){
+  it("calls props.specActions.setScheme() when no currentScheme is selected", function(){
+
+    let setSchemeSpy = jest.fn()
+
+    // Given
+    let props = {
+      specActions: {
+        setScheme: setSchemeSpy
+      },
+      schemes: fromJS([
+        "http",
+        "https"
+      ]),
+      currentScheme: undefined,
+      path: "/test",
+      method: "get"
+    }
+
+    // When
+    let wrapper = shallow(<Schemes {...props}/>)
+
+    // Then currentScheme should default to first scheme in options list
+    expect(props.specActions.setScheme).toHaveBeenCalledWith("http", "/test" , "get")
+
+    // When the currentScheme is no longer in the list of options
+    props.schemes = fromJS([
+      "https"
+    ])
+    wrapper.setProps(props)
+
+    // Then currentScheme should default to first scheme in options list, again
+    expect(props.specActions.setScheme).toHaveBeenCalledWith("https", "/test", "get")
+  })
+
+  it("doesn't call props.specActions.setScheme() when schemes hasn't changed", function(){
+
+    let setSchemeSpy = jest.fn()
+
+    // Given
+    let props = {
+      specActions: {
+        setScheme: setSchemeSpy
+      },
+      schemes: fromJS([
+        "http",
+        "https"
+      ]),
+      currentScheme: "https"
+    }
+
+    // When
+    let wrapper = shallow(<Schemes {...props}/>)
+
+    // Should be called initially, to set the global state
+    expect(setSchemeSpy.mock.calls.length).toEqual(1)
+
+    // After an update
+    wrapper.instance().componentWillReceiveProps(props)
+
+    // Should not be called again, since `currentScheme` is in schemes
+    expect(setSchemeSpy.mock.calls.length).toEqual(1)
+  })
+})