test: add tests to @stdlib/string/format-interpolate

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---

Author: piyxsh31

lib/node_modules/@stdlib/string/base/format-interpolate/test/test.format_integer.js

@@ -168,3 +168,49 @@ tape( 'the function returns an integer-formatted token argument (precision)', fu
 
 	t.end();
 });
+
+tape( 'the function throws an error for non-numeric input', function test( t ) {
+	var token;
+
+	token = {
+		'specifier': 'd',
+		'arg': 'abc'
+	};
+
+	t.throws(function util() {
+		formatInteger( token );
+	}, Error, 'returns expected error' );
+
+	t.end();
+});
+
+tape( 'the function coerces non-finite numeric input to empty string', function test( t ) {
+	var expected;
+	var actual;
+	var token;
+
+	expected = '';
+
+	token = {
+		'specifier': 'd',
+		'arg': NaN
+	};
+	actual = formatInteger( token );
+	t.strictEqual( actual, expected, 'returns expected empty string' );
+
+	token = {
+		'specifier': 'd',
+		'arg': Infinity
+	};
+	actual = formatInteger( token );
+	t.strictEqual( actual, expected, 'returns expected empty string' );
+
+	token = {
+		'specifier': 'd',
+		'arg': -Infinity
+	};
+	actual = formatInteger( token );
+	t.strictEqual( actual, expected, 'returns expected empty string' );
+
+	t.end();
+});