[backend:test] Add simple tests for emoji rendering

backend/src/test/scala/io/github/nwtgck/gh_card/emoji/EmojiRendererSpec.scala

@@ -0,0 +1,23 @@
+package io.github.nwtgck.gh_card.emoji
+
+import org.scalatest.{FunSpec, Matchers}
+
+class EmojiRendererSpec extends FunSpec with Matchers {
+  describe("EmojiRendererSpec") {
+    it("should render") {
+      val actual = EmojiRenderer.render("hello :tada: world")
+      val expect = "hello 🎉 world"
+      actual shouldBe expect
+    }
+    it("should render with many spaces") {
+      val actual = EmojiRenderer.render("hello  :tada:    world")
+      val expect = "hello  🎉    world"
+      actual shouldBe expect
+    }
+    it("should render with space/tab mixed") {
+      val actual = EmojiRenderer.render("hello :tada:\tworld")
+      val expect = "hello 🎉\tworld"
+      actual shouldBe expect
+    }
+  }
+}