diff --git a/test/function/string/format.test.js b/test/function/string/format.test.js
index 216d9f750..d69061297 100644
--- a/test/function/string/format.test.js
+++ b/test/function/string/format.test.js
@@ -121,6 +121,22 @@ describe('format', function () {
       assert.strictEqual(math.format(1.24, { notation: 'engineering', precision: 3 }), '1.24e+0')
 
       // less significant figures than precision, need to add zeros
+      assert.strictEqual(math.format(-1e12, { notation: 'engineering', precision: 3 }), '-1.00e+12')
+      assert.strictEqual(math.format(-1e11, { notation: 'engineering', precision: 3 }), '-100e+9')
+      assert.strictEqual(math.format(-1e10, { notation: 'engineering', precision: 3 }), '-10.0e+9')
+      assert.strictEqual(math.format(-1e9, { notation: 'engineering', precision: 3 }), '-1.00e+9')
+      assert.strictEqual(math.format(1e12, { notation: 'engineering', precision: 3 }), '1.00e+12')
+      assert.strictEqual(math.format(1e11, { notation: 'engineering', precision: 3 }), '100e+9')
+      assert.strictEqual(math.format(1e10, { notation: 'engineering', precision: 3 }), '10.0e+9')
+      assert.strictEqual(math.format(1e9, { notation: 'engineering', precision: 3 }), '1.00e+9')
+      assert.strictEqual(math.format(1e12, { notation: 'engineering', precision: 2 }), '1.0e+12')
+      assert.strictEqual(math.format(1e11, { notation: 'engineering', precision: 2 }), '100e+9')
+      assert.strictEqual(math.format(1e10, { notation: 'engineering', precision: 2 }), '10e+9')
+      assert.strictEqual(math.format(1e9, { notation: 'engineering', precision: 2 }), '1.0e+9')
+      assert.strictEqual(math.format(1e12, { notation: 'engineering', precision: 1 }), '1e+12')
+      assert.strictEqual(math.format(1e11, { notation: 'engineering', precision: 1 }), '100e+9')
+      assert.strictEqual(math.format(1e10, { notation: 'engineering', precision: 1 }), '10e+9')
+      assert.strictEqual(math.format(1e9, { notation: 'engineering', precision: 1 }), '1e+9')
       assert.strictEqual(math.format(10e3, { notation: 'engineering', precision: 2 }), '10e+3')
       assert.strictEqual(math.format(10e3, { notation: 'engineering', precision: 1 }), '10e+3')
       assert.strictEqual(math.format(100e3, { notation: 'engineering', precision: 2 }), '100e+3')
@@ -132,6 +148,18 @@ describe('format', function () {
       assert.strictEqual(math.format(10e-3, { notation: 'engineering', precision: 2 }), '10e-3')
       assert.strictEqual(math.format(100e-3, { notation: 'engineering', precision: 2 }), '100e-3')
       assert.strictEqual(math.format(100e-3, { notation: 'engineering', precision: 1 }), '100e-3')
+      assert.strictEqual(math.format(1e-3, { notation: 'engineering', precision: 1 }), '1e-3')
+      assert.strictEqual(math.format(1e-4, { notation: 'engineering', precision: 1 }), '100e-6')
+      assert.strictEqual(math.format(1e-5, { notation: 'engineering', precision: 1 }), '10e-6')
+      assert.strictEqual(math.format(1e-6, { notation: 'engineering', precision: 1 }), '1e-6')
+      assert.strictEqual(math.format(1e-3, { notation: 'engineering', precision: 3 }), '1.00e-3')
+      assert.strictEqual(math.format(1e-4, { notation: 'engineering', precision: 3 }), '100e-6')
+      assert.strictEqual(math.format(1e-5, { notation: 'engineering', precision: 3 }), '10.0e-6')
+      assert.strictEqual(math.format(1e-6, { notation: 'engineering', precision: 3 }), '1.00e-6')
+      assert.strictEqual(math.format(-1e-3, { notation: 'engineering', precision: 3 }), '-1.00e-3')
+      assert.strictEqual(math.format(-1e-4, { notation: 'engineering', precision: 3 }), '-100e-6')
+      assert.strictEqual(math.format(-1e-5, { notation: 'engineering', precision: 3 }), '-10.0e-6')
+      assert.strictEqual(math.format(-1e-6, { notation: 'engineering', precision: 3 }), '-1.00e-6')
     })
   })
 
@@ -216,6 +244,22 @@ describe('format', function () {
         assert.strictEqual(math.format(bignumber(1.24), { notation: 'engineering', precision: 3 }), '1.24e+0')
 
         // less significant figures than precision, need to add zeros
+        assert.strictEqual(math.format(bignumber(-1e12), { notation: 'engineering', precision: 3 }), '-1.00e+12')
+        assert.strictEqual(math.format(bignumber(-1e11), { notation: 'engineering', precision: 3 }), '-100e+9')
+        assert.strictEqual(math.format(bignumber(-1e10), { notation: 'engineering', precision: 3 }), '-10.0e+9')
+        assert.strictEqual(math.format(bignumber(-1e9), { notation: 'engineering', precision: 3 }), '-1.00e+9')
+        assert.strictEqual(math.format(bignumber(1e12), { notation: 'engineering', precision: 3 }), '1.00e+12')
+        assert.strictEqual(math.format(bignumber(1e11), { notation: 'engineering', precision: 3 }), '100e+9')
+        assert.strictEqual(math.format(bignumber(1e10), { notation: 'engineering', precision: 3 }), '10.0e+9')
+        assert.strictEqual(math.format(bignumber(1e9), { notation: 'engineering', precision: 3 }), '1.00e+9')
+        assert.strictEqual(math.format(bignumber(1e12), { notation: 'engineering', precision: 2 }), '1.0e+12')
+        assert.strictEqual(math.format(bignumber(1e11), { notation: 'engineering', precision: 2 }), '100e+9')
+        assert.strictEqual(math.format(bignumber(1e10), { notation: 'engineering', precision: 2 }), '10e+9')
+        assert.strictEqual(math.format(bignumber(1e9), { notation: 'engineering', precision: 2 }), '1.0e+9')
+        assert.strictEqual(math.format(bignumber(1e12), { notation: 'engineering', precision: 1 }), '1e+12')
+        assert.strictEqual(math.format(bignumber(1e11), { notation: 'engineering', precision: 1 }), '100e+9')
+        assert.strictEqual(math.format(bignumber(1e10), { notation: 'engineering', precision: 1 }), '10e+9')
+        assert.strictEqual(math.format(bignumber(1e9), { notation: 'engineering', precision: 1 }), '1e+9')
         assert.strictEqual(math.format(bignumber(10e3), { notation: 'engineering', precision: 2 }), '10e+3')
         assert.strictEqual(math.format(bignumber(10e3), { notation: 'engineering', precision: 1 }), '10e+3')
         assert.strictEqual(math.format(bignumber(100e3), { notation: 'engineering', precision: 2 }), '100e+3')
@@ -227,6 +271,26 @@ describe('format', function () {
         assert.strictEqual(math.format(bignumber(10e-3), { notation: 'engineering', precision: 2 }), '10e-3')
         assert.strictEqual(math.format(bignumber(100e-3), { notation: 'engineering', precision: 2 }), '100e-3')
         assert.strictEqual(math.format(bignumber(100e-3), { notation: 'engineering', precision: 1 }), '100e-3')
+        assert.strictEqual(math.format(bignumber(1e-3), { notation: 'engineering', precision: 1 }), '1e-3')
+        assert.strictEqual(math.format(bignumber(1e-4), { notation: 'engineering', precision: 1 }), '100e-6')
+        assert.strictEqual(math.format(bignumber(1e-5), { notation: 'engineering', precision: 1 }), '10e-6')
+        assert.strictEqual(math.format(bignumber(1e-6), { notation: 'engineering', precision: 1 }), '1e-6')
+        assert.strictEqual(math.format(bignumber(1e-3), { notation: 'engineering', precision: 3 }), '1.00e-3')
+        assert.strictEqual(math.format(bignumber(1e-4), { notation: 'engineering', precision: 3 }), '100e-6')
+        assert.strictEqual(math.format(bignumber(1e-5), { notation: 'engineering', precision: 3 }), '10.0e-6')
+        assert.strictEqual(math.format(bignumber(1e-6), { notation: 'engineering', precision: 3 }), '1.00e-6')
+        assert.strictEqual(math.format(bignumber(-1e-3), { notation: 'engineering', precision: 3 }), '-1.00e-3')
+        assert.strictEqual(math.format(bignumber(-1e-4), { notation: 'engineering', precision: 3 }), '-100e-6')
+        assert.strictEqual(math.format(bignumber(-1e-5), { notation: 'engineering', precision: 3 }), '-10.0e-6')
+        assert.strictEqual(math.format(bignumber(-1e-6), { notation: 'engineering', precision: 3 }), '-1.00e-6')
+        assert.strictEqual(math.format(bignumber('12345600000000'), { notation: 'engineering', precision: 3 }), '12.3e+12')
+        assert.strictEqual(math.format(bignumber('12345600000000'), { notation: 'engineering', precision: 16 }), '12.34560000000000e+12')
+        assert.strictEqual(math.format(bignumber('12345678901234.56789'), { notation: 'engineering', precision: 3 }), '12.3e+12')
+        assert.strictEqual(math.format(bignumber('12345678901234.56789'), { notation: 'engineering', precision: 16 }), '12.34567890123457e+12')
+        assert.strictEqual(math.format(bignumber('0.000000000000123456'), { notation: 'engineering', precision: 3 }), '123e-15')
+        assert.strictEqual(math.format(bignumber('0.000000000000123456'), { notation: 'engineering', precision: 16 }), '123.4560000000000e-15')
+        assert.strictEqual(math.format(bignumber('0.0000000000001234567890123456789'), { notation: 'engineering', precision: 3 }), '123e-15')
+        assert.strictEqual(math.format(bignumber('0.0000000000001234567890123456789'), { notation: 'engineering', precision: 16 }), '123.4567890123457e-15')
       })
     })
   })