Migrated tests to jest

Used jest-codemods to migrate, will have to pass everything by hand before we can merge.

test/sumPower/sumPower.js

@@ -1,6 +0,0 @@
-const sumPower = (end, power = 2, start = 1) =>
-Array(end + 1 - start)
-.fill(0)
-.map((x, i) => (i + start) ** power)
-.reduce((a, b) => a + b, 0);
-module.exports = sumPower;