test: add signed zero tests

---
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---

Author: kgryte

lib/node_modules/@stdlib/blas/ext/base/dnansumpw/test/test.ndarray.js

@@ -22,6 +22,7 @@
 
 var tape = require( 'tape' );
 var Float64Array = require( '@stdlib/array/float64' );
+var isNegativeZero = require( '@stdlib/math/base/assert/is-negative-zero' );
 var dnansumpw = require( './../lib/ndarray.js' );
 
 
@@ -96,6 +97,17 @@ tape( 'the function calculates the sum of strided array elements (ignoring NaN v
 	t.end();
 });
 
+tape( 'the function preserves the sign of zero', function test( t ) {
+	var x;
+	var v;
+
+	x = new Float64Array( [ -0.0, -0.0, -0.0, -0.0, -0.0 ] );
+	v = dnansumpw( x.length, x, 1, 0 );
+	t.strictEqual( isNegativeZero( v ), true, 'returns expected value' );
+
+	t.end();
+});
+
 tape( 'if provided an `N` parameter less than or equal to `0`, the function returns `0.0`', function test( t ) {
 	var x;
 	var v;

lib/node_modules/@stdlib/blas/ext/base/dnansumpw/test/test.ndarray.native.js

@@ -23,6 +23,7 @@
 var resolve = require( 'path' ).resolve;
 var tape = require( 'tape' );
 var Float64Array = require( '@stdlib/array/float64' );
+var isNegativeZero = require( '@stdlib/math/base/assert/is-negative-zero' );
 var tryRequire = require( '@stdlib/utils/try-require' );
 
 
@@ -105,6 +106,17 @@ tape( 'the function calculates the sum of strided array elements (ignoring NaN v
 	t.end();
 });
 
+tape( 'the function preserves the sign of zero', opts, function test( t ) {
+	var x;
+	var v;
+
+	x = new Float64Array( [ -0.0, -0.0, -0.0, -0.0, -0.0 ] );
+	v = dnansumpw( x.length, x, 1, 0 );
+	t.strictEqual( isNegativeZero( v ), true, 'returns expected value' );
+
+	t.end();
+});
+
 tape( 'if provided an `N` parameter less than or equal to `0`, the function returns `0.0`', opts, function test( t ) {
 	var x;
 	var v;