text: /**
  * @license Apache-2.0
  *
  * Copyright (c) 2018 The Stdlib Authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *    http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
  
  'use strict';
  
  // MODULES //
  
  var tape = require( 'tape' );
  var isnan = require( '@stdlib/math/base/assert/is-nan' );
  var factorial = require( '@stdlib/math/base/special/factorial' );
  var incrspace = require( '@stdlib/math/utils/incrspace' );
  var abs = require( '@stdlib/math/base/special/abs' );
  var ln = require( '@stdlib/math/base/special/ln' );
  var NINF = require( '@stdlib/constants/math/float64-ninf' );
  var PINF = require( '@stdlib/constants/math/float64-pinf' );
  var EPS = require( '@stdlib/constants/math/float64-eps' );
  var factorialln = require( './../lib' );
  
  
  // FIXTURES //
  
  var veryLargePositive = require( './fixtures/julia/very_large_positive.json' );
  var largePositive = require( './fixtures/julia/large_positive.json' );
  var mediumPositive = require( './fixtures/julia/medium_positive.json' );
  var smallPositive = require( './fixtures/julia/small_positive.json' );
  
  
  // TESTS //
  
  tape( 'main export is a function', function test( t ) {
  	t.ok( true, __filename );
  	t.equal( typeof factorialln, 'function', 'main export is a function' );
  	t.end();
  });
  
  tape( 'if provided a negative integer, the function returns `NaN`', function test( t ) {
  	var values;
  	var v;
  	var i;
  
  	values = incrspace( -1.0, -500.0, -1.0 );
  	for ( i = 0; i < values.length; i++ ) {
  		v = factorialln( values[ i ] );
  		t.equal( isnan( v ), true, 'returns NaN when provided ' + values[ i ] );
  	}
  	t.end();
  });
  
  tape( 'if provided negative infinity, the function returns `NaN`', function test( t ) {
  	var v = factorialln( NINF );
  	t.strictEqual( isnan( v ), true, 'returns NaN when provided negative infinity' );
  	t.end();
  });
  
  tape( 'if provided positive infinity, the function returns `+infinity`', function test( t ) {
  	var v = factorialln( PINF );
  	t.ok( v, PINF, 'returns +infinity when provided +infinity' );
  	t.end();
  });
  
  tape( 'if provided `NaN`, the function returns `NaN`', function test( t ) {
  	var v = factorialln( NaN );
  	t.equal( isnan( v ), true, 'returns NaN when provided a NaN' );
  	t.end();
  });
  
  tape( 'the function evaluates the natural logarithm of the factorial of `x` (very large positive integers)', function test( t ) {
  	var expected;
  	var delta;
  	var tol;
  	var x;
  	var y;
  	var i;
  
  	expected = veryLargePositive.expected;
  	x = veryLargePositive.x;
  
  	for ( i = 0; i < x.length; i++ ) {
  		y = factorialln( x[i] );
  		if ( y === expected[i] ) {
  			t.equal( y, expected[i], 'x: '+x[i]+', y: '+y+', expected: '+expected[i] );
  		} else {
  			delta = abs( y - expected[i] );
  			tol = EPS * abs( expected[i] );
  			t.equal( delta <= tol, true, 'within tolerance. x: '+x[i]+'. y: '+y+'. E: '+expected[i]+'. Δ: '+delta+'. Tolerance: '+tol+'.' );
  		}
  	}
  	t.end();
  });
  
  tape( 'the function evaluates the natural logarithm of the factorial of `x` (large positive integers)', function test( t ) {
  	var expected;
  	var delta;
  	var tol;
  	var x;
  	var y;
  	var i;
  
  	expected = largePositive.expected;
  	x = largePositive.x;
  
  	for ( i = 0; i < x.length; i++ ) {
  		y = factorialln( x[i] );
  		if ( y === expected[i] ) {
  			t.equal( y, expected[i], 'x: '+x[i]+', y: '+y+', expected: '+expected[i] );
  		} else {
  			delta = abs( y - expected[i] );
  			tol = EPS * abs( expected[i] );
  			t.equal( delta <= tol, true, 'within tolerance. x: '+x[i]+'. y: '+y+'. E: '+expected[i]+'. Δ: '+delta+'. Tolerance: '+tol+'.' );
  		}
  	}
  	t.end();
  });
  
  tape( 'the function evaluates the natural logarithm of the factorial of `x` (medium positive values)', function test( t ) {
  	var expected;
  	var delta;
  	var tol;
  	var x;
  	var y;
  	var i;
  
  	expected = mediumPositive.expected;
  	x = mediumPositive.x;
  	for ( i = 0; i < x.length; i++ ) {
  		y = factorialln( x[i] );
  		if ( y === expected[i] ) {
  			t.equal( y, expected[i], 'x: '+x[i]+', y: '+y+', expected: '+expected[i] );
  		} else {
  			delta = abs( y - expected[i] );
  			tol = EPS * abs( expected[i] );
  			t.equal( delta <= tol, true, 'within tolerance. x: '+x[i]+'. y: '+y+'. E: '+expected[i]+'. Δ: '+delta+'. Tolerance: '+tol+'.' );
  		}
  	}
  	t.end();
  });
  
  tape( 'the function evaluates the natural logarithm of the factorial of `x` (small positive values)', function test( t ) {
  	var expected;
  	var delta;
  	var tol;
  	var x;
  	var y;
  	var i;
  
  	expected = smallPositive.expected;
  	x = smallPositive.x;
  	for ( i = 0; i < x.length; i++ ) {
  		y = factorialln( x[i] );
  		if ( y === expected[i] ) {
  			t.equal( y, expected[i], 'x: '+x[i]+', y: '+y+', expected: '+expected[i] );
  		} else {
  			delta = abs( y - expected[i] );
  			tol = EPS * abs( expected[i] );
  			t.equal( delta <= tol, true, 'within tolerance. x: '+x[i]+'. y: '+y+'. E: '+expected[i]+'. Δ: '+delta+'. Tolerance: '+tol+'.' );
  		}
  	}
  	t.end();
  });
  
  tape( 'the function returns a value almost equal to `ln( factorial( x )` for `x` in `[0,171]', function test( t ) {
  	var expected;
  	var values;
  	var delta;
  	var tol;
  	var v;
  	var i;
  
  	values = incrspace( 0.0, 171.0, 0.5 );
  	for ( i = 0; i < values.length; i++ ) {
  		v = factorialln( values[ i ] );
  		expected = ln( factorial( values[ i ] ) );
  		delta = abs( v - expected );
  		tol = 4.0 * EPS * abs( expected );
  		t.ok( delta <= tol, 'within tolerance. x: ' + values[ i ] + '. Value: ' + v + '. Expected: ' + expected + '. Tolerance: ' + tol + '. Delta: ' + delta + '.' );
  	}
  	t.end();
  });
  