test: adds missing test cases

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---

Author: rahulptl165

lib/node_modules/@stdlib/stats/base/nanmeanpn/docs/types/test.ts

@@ -26,6 +26,7 @@ import nanmeanpn = require( './index' );
 {
 	const x = new Float64Array( 10 );
 
+	nanmeanpn( x.length, x, 1 ); // $ExpectType number
 	nanmeanpn( x.length, new AccessorArray( x ), 1 ); // $ExpectType number
 }
 
@@ -85,6 +86,7 @@ import nanmeanpn = require( './index' );
 {
 	const x = new Float64Array( 10 );
 
+	nanmeanpn.ndarray( x.length, x, 1, 0 ); // $ExpectType number
 	nanmeanpn.ndarray( x.length, new AccessorArray( x ), 1, 0 ); // $ExpectType number
 }
 

lib/node_modules/@stdlib/stats/base/nanmeanpn/test/test.nanmeanpn.js

@@ -215,6 +215,18 @@ tape( 'if provided a `stride` parameter equal to `0`, the function returns the f
 	t.end();
 });
 
+tape( 'if provided a `stride` parameter equal to `0`, the function returns the first element (accessors)', function test( t ) {
+	var x;
+	var v;
+
+	x = [ 1.0, -2.0, -4.0, 5.0, 3.0 ];
+
+	v = nanmeanpn( x.length, toAccessorArray( x ), 0 );
+	t.strictEqual( v, 1.0, 'returns expected value' );
+
+	t.end();
+});
+
 tape( 'the function supports view offsets', function test( t ) {
 	var x0;
 	var x1;

lib/node_modules/@stdlib/stats/base/nanmeanpn/test/test.ndarray.js

@@ -214,6 +214,18 @@ tape( 'if provided a `stride` parameter equal to `0`, the function returns the f
 	t.end();
 });
 
+tape( 'if provided a `stride` parameter equal to `0`, the function returns the first indexed element (accessors)', function test( t ) {
+	var x;
+	var v;
+
+	x = [ 1.0, -2.0, -4.0, 5.0, 3.0 ];
+
+	v = nanmeanpn( x.length, toAccessorArray( x ), 0, 0 );
+	t.strictEqual( v, 1.0, 'returns expected value' );
+
+	t.end();
+});
+
 tape( 'the function supports an `offset` parameter', function test( t ) {
 	var x;
 	var v;