test: add tests for DataType instances

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---

Author: kgryte

lib/node_modules/@stdlib/ndarray/base/dtype-char/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 dtypeChar = require( './../lib' );
 
 
@@ -91,7 +93,7 @@ tape( 'the function returns an object mapping data type strings to single letter
 	t.end();
 });
 
-tape( 'the function returns the single letter character abbreviation for an underlying array data type', function test( t ) {
+tape( 'the function returns the single letter character abbreviation for an underlying array data type (data type string)', function test( t ) {
 	var expected;
 	var ch;
 	var i;
@@ -123,8 +125,73 @@ tape( 'the function returns the single letter character abbreviation for an unde
 	t.end();
 });
 
+tape( 'the function returns the single letter character abbreviation for an underlying array data type (data type instance)', function test( t ) {
+	var expected;
+	var dtypes;
+	var ch;
+	var i;
+
+	dtypes = [
+		'float64',
+		'float32',
+		'float16',
+		'int8',
+		'uint8',
+		'uint8c',
+		'int16',
+		'uint16',
+		'int32',
+		'uint32',
+		'binary',
+		'generic',
+		'complex32',
+		'complex64',
+		'complex128',
+		'bool'
+	];
+
+	expected = [
+		'd',
+		'f',
+		'h',
+		's',
+		'b',
+		'a',
+		'k',
+		't',
+		'i',
+		'u',
+		'r',
+		'o',
+		'j',
+		'c',
+		'z',
+		'x'
+	];
+	for ( i = 0; i < dtypes.length; i++ ) {
+		ch = dtypeChar( new DataType( dtypes[ i ] ) );
+		t.strictEqual( ch, expected[ i ], 'returns '+expected[i]+' when provided '+dtypes[i] );
+	}
+	t.end();
+});
+
 tape( 'the function returns `null` if provided an unknown/unsupported data type', function test( t ) {
-	var ch = dtypeChar( 'foobar' );
+	var schema;
+	var ch;
+
+	ch = dtypeChar( 'foobar' );
+	t.strictEqual( ch, null, 'returns expected value' );
+
+	schema = [
+		{
+			'name': 'foo',
+			'type': 'float64'
+		}
+	];
+	ch = dtypeChar( structFactory( schema ) );
+	t.strictEqual( ch, null, 'returns expected value' );
+
+	ch = dtypeChar( new DataType( structFactory( schema ) ) );
 	t.strictEqual( ch, null, 'returns expected value' );
 	t.end();
 });