test(switch): add tests

Author: Sergei Orlov

tests/Switch.spec.ts

@@ -0,0 +1,52 @@
+import match, { Switch } from "../src";
+
+describe("Switch", () => {
+  it("should exist", () => {
+    expect(Switch).not.toBe(undefined);
+  });
+
+  describe("Switch.for", () => {
+    it("should create an instance of Switch", () => {
+      expect(Switch.for("")).toBeInstanceOf(Switch);
+    });
+  });
+
+  describe("case/default", () => {
+    it("should defer execution until default is called", () => {
+      expect(match("asdf").case("", () => 123)).toBeInstanceOf(Switch);
+    });
+
+    it("should return value if matched by equation", () => {
+      expect(
+        match("")
+          .case("", 123)
+          .default(345),
+      ).toEqual(123);
+    });
+
+    it("should return value if matched by predicate function", () => {
+      expect(
+        match("asdf")
+          .case(x => x == "asdf", 123)
+          .default(345),
+      ).toEqual(123);
+    });
+
+    it("should return default value if not matched", () => {
+      expect(
+        match("asdf")
+          .case("", 123)
+          .default(234),
+      ).toEqual(234);
+    });
+
+    it("should preserve the first match and its value", () => {
+      expect(
+        match("asdf")
+          .case("asdf", 123)
+          .case("asdf", 234)
+          .default(345),
+      ).toEqual(123);
+    });
+  });
+});