Improve private key import tests

test/unit/app/account-import-strategies.spec.js

@@ -7,11 +7,35 @@ describe('Account Import Strategies', function () {
   const privkey = '0x4cfd3e90fc78b0f86bf7524722150bb8da9c60cd532564d7ff43f5716514f553'
   const json = '{"version":3,"id":"dbb54385-0a99-437f-83c0-647de9f244c3","address":"a7f92ce3fba24196cf6f4bd2e1eb3db282ba998c","Crypto":{"ciphertext":"bde13d9ade5c82df80281ca363320ce254a8a3a06535bbf6ffdeaf0726b1312c","cipherparams":{"iv":"fbf93718a57f26051b292f072f2e5b41"},"cipher":"aes-128-ctr","kdf":"scrypt","kdfparams":{"dklen":32,"salt":"7ffe00488319dec48e4c49a120ca49c6afbde9272854c64d9541c83fc6acdffe","n":8192,"r":8,"p":1},"mac":"2adfd9c4bc1cdac4c85bddfb31d9e21a684e0e050247a70c5698facf6b7d4681"}}'
 
-  describe('private key import', function () {
+  describe.only('private key import', function () {
     it('imports a private key and strips 0x prefix', async function () {
       const importPrivKey = await accountImporter.importAccount('Private Key', [ privkey ])
       assert.equal(importPrivKey, ethUtil.stripHexPrefix(privkey))
     })
+
+    it('throws an error for empty string private key', async () => {
+      assert.throws(async () => {
+        const privKey = await accountImporter.importAccount('Private Key', [ '' ])
+      })
+    })
+
+    it('throws an error for undefined string private key', async () => {
+      assert.throws(async () => {
+        const privKey = await accountImporter.importAccount('Private Key', [ undefined ])
+      })
+    })
+
+    it('throws an error for undefined string private key', async () => {
+      assert.throws(async () => {
+        const privKey = await accountImporter.importAccount('Private Key', [])
+      })
+    })
+
+    it('throws an error for invalid private key', async () => {
+      assert.throws(async () => {
+        const privKey = await accountImporter.importAccount('Private Key', [ 'popcorn' ])
+      })
+    })
   })
 
   describe('JSON keystore import', function () {