diff --git a/test/arithmetic-test.js b/test/arithmetic-test.js
index 24fb4ca..7dc0c12 100644
--- a/test/arithmetic-test.js
+++ b/test/arithmetic-test.js
@@ -1,6 +1,6 @@
 var assert = require('assert');
 var BN = require('../').BN;
-var fixtures = require('./fixtures');
+var fixtures = require('./fixtures/dh-groups');
 
 describe('BN.js/Arithmetic', function() {
   describe('.add()', function() {
@@ -183,8 +183,8 @@ describe('BN.js/Arithmetic', function() {
     });
 
     it('should regress mul big numbers', function() {
-      var q = fixtures.dhGroups.p17.q;
-      var qs = fixtures.dhGroups.p17.qs;
+      var q = fixtures.p17.q;
+      var qs = fixtures.p17.qs;
 
       var q = new BN(q, 16);
       assert.equal(q.sqr().toString(16), qs);
diff --git a/test/binary-test.js b/test/binary-test.js
index 9a0673a..b3a29b0 100644
--- a/test/binary-test.js
+++ b/test/binary-test.js
@@ -1,6 +1,5 @@
 var assert = require('assert');
 var BN = require('../').BN;
-var fixtures = require('./fixtures');
 
 describe('BN.js/Binary', function() {
   describe('.shl()', function() {
diff --git a/test/constructor-test.js b/test/constructor-test.js
index a5f6c3f..1896eaf 100644
--- a/test/constructor-test.js
+++ b/test/constructor-test.js
@@ -1,6 +1,5 @@
 var assert = require('assert');
 var BN = require('../').BN;
-var fixtures = require('./fixtures');
 
 describe('BN.js/Constructor', function() {
   describe('with Smi input', function() {
diff --git a/test/fixtures/bn.json b/test/fixtures/bn.json
new file mode 100644
index 0000000..0d6eb44
--- /dev/null
+++ b/test/fixtures/bn.json
@@ -0,0 +1,105 @@
+{
+  "valid": [
+    {
+      "dec": "0",
+      "hex": "00"
+    },
+    {
+      "dec": "1",
+      "hex": "01"
+    },
+    {
+      "dec": "-1",
+      "hex": "ff"
+    },
+    {
+      "dec": "127",
+      "hex": "7f"
+    },
+    {
+      "dec": "-127",
+      "hex": "81"
+    },
+    {
+      "dec": "128",
+      "hex": "80"
+    },
+    {
+      "dec": "-128",
+      "hex": "80"
+    },
+    {
+      "dec": "255",
+      "hex": "ff"
+    },
+    {
+      "dec": "-255",
+      "hex": "ff01"
+    },
+    {
+      "dec": "16300",
+      "hex": "3fac"
+    },
+    {
+      "dec": "-16300",
+      "hex": "c054"
+    },
+    {
+      "dec": "62300",
+      "hex": "f35c"
+    },
+    {
+      "dec": "-62300",
+      "hex": "ff0ca4"
+    },
+    {
+      "dec": "158798437896437949616241483468158498679",
+      "hex": "77777777777777777777777777777777"
+    },
+    {
+      "dec": "115792089237316195423570985008687907852837564279074904382605163141518161494336",
+      "hex": "fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364140"
+    },
+    {
+      "dec": "48968302285117906840285529799176770990048954789747953886390402978935544927851",
+      "hex": "6c4313b03f2e7324d75e642f0ab81b734b724e13fec930f309e222470236d66b"
+    }
+  ],
+  "invalid": [
+    {
+      "description": "non-decimal string",
+      "dec": "invalid"
+    },
+    {
+      "description": "non-hex string",
+      "hex": "invalid"
+    },
+    {
+      "description": "incomplete hex",
+      "hex": "ffffd0a"
+    },
+    {
+      "description": "non-decimal alphabet",
+      "dec": "c2F0b3NoaQo="
+    },
+    {
+      "description": "non-hex alphabet",
+      "hex": "c2F0b3NoaQo="
+    },
+    {
+      "description": "internal whitespace",
+      "dec": "11111 11111",
+      "hex": "11111 11111"
+    },
+    {
+      "description": "leading whitespace",
+      "dec": " 1111111111",
+      "hex": " 1111111111"
+    },
+    {
+      "description": "trailing whitespace",
+      "dec": "1111111111 ",
+      "hex": "1111111111 "
+    }
+  ]
+}
diff --git a/test/fixtures.js b/test/fixtures/dh-groups.js
similarity index 99%
rename from test/fixtures.js
rename to test/fixtures/dh-groups.js
index 29442d9..183eece 100644
--- a/test/fixtures.js
+++ b/test/fixtures/dh-groups.js
@@ -1,4 +1,4 @@
-exports.dhGroups = {
+module.exports = {
   p16: {
     prime: 'ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd1' +
       '29024e088a67cc74020bbea63b139b22514a08798e3404dd' +
diff --git a/test/pummel/dh-group-test.js b/test/pummel/dh-group-test.js
index dd6481f..54fb139 100644
--- a/test/pummel/dh-group-test.js
+++ b/test/pummel/dh-group-test.js
@@ -1,9 +1,8 @@
 var assert = require('assert');
 var BN = require('../../').BN;
-var fixtures = require('../fixtures');
+var groups = require('../fixtures/dh-groups');
 
 describe('BN.js/Slow DH test', function() {
-  var groups = fixtures.dhGroups;
   Object.keys(groups).forEach(function(name) {
     it('should match public key for ' + name + ' group', function() {
       var group = groups[name];
diff --git a/test/red-test.js b/test/red-test.js
index 9c348b6..a1243be 100644
--- a/test/red-test.js
+++ b/test/red-test.js
@@ -1,6 +1,5 @@
 var assert = require('assert');
 var BN = require('../').BN;
-var fixtures = require('./fixtures');
 
 describe('BN.js/Reduction context', function() {
   function testMethod(name, fn) {
diff --git a/test/utils-test.js b/test/utils-test.js
index c033aa7..a9b73c5 100644
--- a/test/utils-test.js
+++ b/test/utils-test.js
@@ -1,25 +1,46 @@
 var assert = require('assert');
 var BN = require('../').BN;
-var fixtures = require('./fixtures');
+var fixtures = require('./fixtures/bn');
 
 describe('BN.js/Utils', function() {
   describe('.toString()', function() {
+    fixtures.valid.forEach(function(f) {
+      it('should return ' + f.dec + ' when built with ' + f.dec, function() {
+        var bi = new BN(f.dec);
+
+        assert.equal(bi.toString(), f.dec);
+      });
+
+      it('should return ' + f.dec + ' when built with ' + f.hex, function() {
+        var bi = new BN(f.hex, 16);
+
+        assert.equal(bi.toString(), f.dec);
+      });
+
+      it('should return big-endian twos complement' +
+         'hex for ' + f.dec, function() {
+        var bi = new BN(f.dec);
+
+        assert.equal(bi.toString('hex'), f.hex);
+      });
+    });
+
     describe('hex padding', function() {
       it('should have length of 8 from leading 15', function() {
         var a = new BN('ffb9602', 16);
-        var b = new Buffer(a.toString('hex', 2), 'hex');
+
         assert.equal(a.toString('hex', 2).length, 8);
       });
 
       it('should have length of 8 from leading zero', function() {
         var a = new BN('fb9604', 16);
-        var b = new Buffer(a.toString('hex', 8), 'hex');
+
         assert.equal(a.toString('hex', 8).length, 8);
       });
 
       it('should have length of 8 from leading zeros', function() {
         var a = new BN(0);
-        var b = new Buffer(a.toString('hex', 8), 'hex');
+
         assert.equal(a.toString('hex', 8).length, 8);
       });
 
@@ -27,7 +48,7 @@ describe('BN.js/Utils', function() {
         var a = new BN(
             'ffb96ff654e61130ba8422f0debca77a0ea74ae5ea8bca9b54ab64aabf01003',
             16);
-        var b = new Buffer(a.toString('hex', 2), 'hex');
+
         assert.equal(a.toString('hex', 2).length, 64);
       });
 
@@ -35,12 +56,42 @@ describe('BN.js/Utils', function() {
         var a = new BN(
             'fb96ff654e61130ba8422f0debca77a0ea74ae5ea8bca9b54ab64aabf01003',
             16);
-        var b = new Buffer(a.toString('hex', 64), 'hex');
+
         assert.equal(a.toString('hex', 64).length, 64);
       });
     });
   });
 
+  describe('.toArray()', function() {
+    fixtures.valid.forEach(function(f) {
+      it('should return a big-endian ' +
+         'twos complement integer for ' + f.dec, function() {
+        var bi = new BN(f.dec);
+        var ba = new Buffer(bi.toArray());
+
+        assert.equal(ba.toString('hex'), f.hex);
+      });
+    });
+
+    fixtures.invalid.forEach(function(f) {
+      if (f.dec) {
+        it('should throw on ' + f.dec, function() {
+          assert.throws(function() {
+            new BN(f.dec);
+          });
+        });
+      }
+
+      if (f.hex) {
+        it('should throw on ' + f.hex, function() {
+          assert.throws(function() {
+            new BN(f.hex, 16);
+          });
+        });
+      }
+    });
+  });
+
   describe('.bitLength()', function() {
     it('should return proper bitLength', function() {
       assert.equal(new BN(0).bitLength(), 0);