test: add tests for DataType instances

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---

Author: kgryte

lib/node_modules/@stdlib/ndarray/base/dtype-desc/test/test.js

@@ -21,6 +21,8 @@
 // MODULES //
 
 var tape = require( 'tape' );
+var DataType = require( '@stdlib/ndarray/dtype-ctor' );
+var structFactory = require( '@stdlib/dstructs/struct' );
 var table = require( './../lib/table.js' );
 var dtypeDesc = require( './../lib' );
 
@@ -73,7 +75,7 @@ tape( 'the function returns an object mapping data type strings to descriptions
 	t.end();
 });
 
-tape( 'the function returns the description for a specified data type', function test( t ) {
+tape( 'the function returns the description for a specified data type (string)', function test( t ) {
 	var expected;
 	var v;
 	var i;
@@ -86,8 +88,37 @@ tape( 'the function returns the description for a specified data type', function
 	t.end();
 });
 
+tape( 'the function returns the description for a specified data type (data type instance)', function test( t ) {
+	var expected;
+	var v;
+	var i;
+
+	for ( i = 0; i < DTYPES.length; i++ ) {
+		v = dtypeDesc( new DataType( DTYPES[ i ] ) );
+		expected = DESC[ DTYPES[ i ] ] || null;
+		t.strictEqual( v, expected, 'returns '+expected+' when provided '+DTYPES[i] );
+	}
+	t.end();
+});
+
 tape( 'the function returns `null` if provided an unknown/unsupported data type', function test( t ) {
-	var v = dtypeDesc( 'foobar' );
+	var schema;
+	var v;
+
+	v = dtypeDesc( 'foobar' );
 	t.strictEqual( v, null, 'returns expected value' );
+
+	schema = [
+		{
+			'name': 'foo',
+			'type': 'float64'
+		}
+	];
+	v = dtypeDesc( structFactory( schema ) );
+	t.strictEqual( v, null, 'returns expected value' );
+
+	v = dtypeDesc( new DataType( structFactory( schema ) ) );
+	t.strictEqual( v, null, 'returns expected value' );
+
 	t.end();
 });