Add repo_loading_file_spec

spec/javascripts/repo/repo_loading_file_spec.js

+import Vue from 'vue';
+import repoLoadingFile from '~/repo/repo_loading_file.vue';
+
+describe('RepoLoadingFile', () => {
+  const RepoLoadingFile = Vue.extend(repoLoadingFile);
+
+  function createComponent(propsData) {
+    return new RepoLoadingFile({
+      propsData,
+    }).$mount();
+  }
+
+  function assertLines(lines) {
+    lines.forEach((line, n) => {
+      const index = n + 1;
+      expect(line.classList.contains(`line-of-code-${index}`)).toBeTruthy();
+    });
+  }
+
+  function assertColumns(columns) {
+    columns.forEach((column) => {
+      const container = column.querySelector('.animation-container');
+      const lines = [...container.querySelectorAll(':scope > div')];
+
+      expect(container).toBeTruthy();
+      expect(lines.length).toEqual(6);
+      assertLines(lines);
+    });
+  }
+
+  it('renders 3 columns of animated LoC', () => {
+    const vm = createComponent({
+      loading: {
+        tree: true,
+      },
+      hasFiles: false,
+    });
+    const columns = [...vm.$el.querySelectorAll('td')];
+
+    expect(columns.length).toEqual(3);
+    assertColumns(columns);
+  });
+
+  it('renders 1 column of animated LoC if isMini', () => {
+    const vm = createComponent({
+      loading: {
+        tree: true,
+      },
+      hasFiles: false,
+      isMini: true,
+    });
+    const columns = [...vm.$el.querySelectorAll('td')];
+
+    expect(columns.length).toEqual(1);
+    assertColumns(columns);
+  });
+
+  it('does not render if tree is not loading', () => {
+    const vm = createComponent({
+      loading: {
+        tree: false,
+      },
+      hasFiles: false,
+    });
+
+    expect(vm.$el.innerHTML).toBeFalsy();
+  });
+
+  it('does not render if hasFiles is true', () => {
+    const vm = createComponent({
+      loading: {
+        tree: true,
+      },
+      hasFiles: true,
+    });
+
+    expect(vm.$el.innerHTML).toBeFalsy();
+  });
+});