test: add complete tests for dgttrf

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Author: aayush0325

lib/node_modules/@stdlib/lapack/base/dgttrf/test/test.dgttrf.js

@@ -164,6 +164,29 @@ tape( 'the function performs the `LU` factorization of a real tri diagonal matri
 	t.end();
 });
 
+tape( 'the function returns a non zero status code when a diagonal element is equal to zero', function test( t ) {
+	var info;
+	var IPIV;
+	var DU2;
+	var DU;
+	var DL;
+	var D;
+	var N;
+
+	N = 3;
+
+	DL = new Float64Array( [ 0.0, 0.0 ] );
+	D = new Float64Array( [ 1.0, 1.0, 0.0 ] );
+	DU = new Float64Array( [ 2.0, 3.0 ] );
+	DU2 = new Float64Array( 1 );
+	IPIV = new Int32Array( 3 );
+
+	info = dgttrf( N, DL, D, DU, DU2, IPIV );
+	t.strictEqual( info, 2, 'returns expected value' );
+
+	t.end();
+});
+
 tape( 'the function leaves the input arrays unchanged when `N` is equal to zero', function test( t ) {
 	var expectedIPIV;
 	var expectedDU2;