algorithm: signum (#1266)

Maths/test/Signum.test.js

@@ -0,0 +1,19 @@
+import { signum } from '../Signum'
+
+describe('The sign of a number', () => {
+  it('Sign of 10', () => {
+    expect(signum(10)).toBe(1)
+  })
+
+  it('Sign of 0', () => {
+    expect(signum(0)).toBe(0)
+  })
+
+  it('Sign of -420', () => {
+    expect(signum(-420)).toBe(-1)
+  })
+
+  it('Sign of NaN', () => {
+    expect(signum(NaN)).toBe(NaN)
+  })
+})