Add shared metric card component

- Adds a reusable container
for displaying metrics in the
analytics space

ee/app/assets/javascripts/analytics/shared/components/metric_card.vue

+<script>
+import { GlCard, GlSkeletonLoading } from '@gitlab/ui';
+
+export default {
+  name: 'MetricCard',
+  components: {
+    GlCard,
+    GlSkeletonLoading,
+  },
+  props: {
+    title: {
+      type: String,
+      required: true,
+    },
+    metrics: {
+      type: Array,
+      required: true,
+    },
+    isLoading: {
+      type: Boolean,
+      required: false,
+      default: false,
+    },
+  },
+};
+</script>
+
+<template>
+  <gl-card>
+    <template #header>
+      <strong ref="title">{{ title }}</strong>
+    </template>
+    <template #default>
+      <gl-skeleton-loading v-if="isLoading" class="h-auto py-3" />
+      <div v-else ref="metricsWrapper" class="d-flex">
+        <div
+          v-for="metric in metrics"
+          :key="metric.key"
+          ref="metricItem"
+          class="flex-grow text-center"
+        >
+          <h3 class="my-2">
+            <template v-if="metric.value === null"
+              >-</template
+            >
+            <template v-else>{{ metric.value }}</template>
+          </h3>
+          <p class="text-secondary gl-font-size-small mb-2">{{ metric.label }}</p>
+        </div>
+      </div>
+    </template>
+  </gl-card>
+</template>

ee/spec/frontend/analytics/shared/components/metric_card_spec.js

+import { mount } from '@vue/test-utils';
+import { GlSkeletonLoading } from '@gitlab/ui';
+import MetricCard from 'ee/analytics/shared/components/metric_card.vue';
+
+const defaultProps = {
+  title: 'My fancy title',
+  metrics: [
+    { key: 'first_metric', value: 10, label: 'First metric' },
+    { key: 'second_metric', value: 20, label: 'Yet another metric' },
+    { key: 'third_metric', value: null, label: 'Metric without value' },
+  ],
+  isLoading: false,
+};
+
+describe('MetricCard', () => {
+  let wrapper;
+
+  const factory = (props = defaultProps) => {
+    wrapper = mount(MetricCard, {
+      propsData: {
+        ...defaultProps,
+        ...props,
+      },
+    });
+  };
+
+  afterEach(() => {
+    wrapper.destroy();
+  });
+
+  const findTitle = () => wrapper.find({ ref: 'title' });
+  const findLoadingIndicator = () => wrapper.find(GlSkeletonLoading);
+  const findMetricsWrapper = () => wrapper.find({ ref: 'metricsWrapper' });
+  const findMetricItem = () => wrapper.findAll({ ref: 'metricItem' });
+
+  describe('template', () => {
+    it('renders the title', () => {
+      factory();
+
+      expect(findTitle().text()).toContain('My fancy title');
+    });
+
+    describe('when isLoading is true', () => {
+      beforeEach(() => {
+        factory({ isLoading: true });
+      });
+
+      it('displays a loading indicator', () => {
+        expect(findLoadingIndicator().exists()).toBe(true);
+      });
+
+      it('does not display the metrics container', () => {
+        expect(findMetricsWrapper().exists()).toBe(false);
+      });
+    });
+
+    describe('when isLoading is false', () => {
+      beforeEach(() => {
+        factory({ isLoading: false });
+      });
+
+      it('does not display a loading indicator', () => {
+        expect(findLoadingIndicator().exists()).toBe(false);
+      });
+
+      it('displays the metrics container', () => {
+        expect(findMetricsWrapper().exists()).toBe(true);
+      });
+
+      it('renders two metrics', () => {
+        expect(findMetricItem()).toHaveLength(3);
+      });
+
+      describe.each`
+        columnIndex | label                     | value
+        ${0}        | ${'First metric'}         | ${10}
+        ${1}        | ${'Yet another metric'}   | ${20}
+        ${2}        | ${'Metric without value'} | ${'-'}
+      `('metric columns', ({ columnIndex, label, value }) => {
+        it(`renders "${label}" as label`, () => {
+          expect(
+            findMetricItem()
+              .at(columnIndex)
+              .text(),
+          ).toContain(label);
+        });
+
+        it(`renders ${value} as value`, () => {
+          expect(
+            findMetricItem()
+              .at(columnIndex)
+              .text(),
+          ).toContain(value);
+        });
+      });
+    });
+  });
+});