Add missing specs for crypto helper class

spec/lib/gitlab/crypto_helper_spec.rb

+require 'spec_helper'
+
+describe Gitlab::CryptoHelper do
+  describe '.sha256' do
+    it 'generates SHA256 digest Base46 encoded' do
+      digest = described_class.sha256('some-value')
+
+      expect(digest).to match %r{^[A-Za-z0-9+/=]+$}
+      expect(digest).to eq digest.strip
+    end
+  end
+
+  describe '.aes256_gcm_encrypt' do
+    it 'is Base64 encoded string without new line character' do
+      encrypted = described_class.aes256_gcm_encrypt('some-value')
+
+      expect(encrypted).to match %r{^[A-Za-z0-9+/=]+$}
+      expect(encrypted).to eq encrypted.strip
+    end
+  end
+
+  describe '.aes256_gcm_decrypt' do
+    let(:encrypted) { described_class.aes256_gcm_encrypt('some-value') }
+
+    it 'correctly decrypts encrypted string' do
+      decrypted = described_class.aes256_gcm_decrypt(encrypted)
+
+      expect(decrypted).to eq 'some-value'
+    end
+
+    it 'decrypts a value when it ends with a new line character' do
+      decrypted = described_class.aes256_gcm_decrypt(encrypted + "\n")
+
+      expect(decrypted).to eq 'some-value'
+    end
+  end
+end