Add a test for nqp::log_n.

Author: pmurias

t/nqp/83-log.t

@@ -0,0 +1,20 @@
+plan(2);
+
+# Basic tests for nqp::log_n
+
+my $log_5 := 940945/584642;
+my $log_one_tenth := -254834/110673;
+
+sub is_approx($got, $expected, $descr =  "$got is approximately $expected") {
+    my $tol := nqp::abs_n($expected) < 1e-6 ?? 1e-5 !! nqp::abs_n($expected) * 1e-6;
+    my $test := nqp::abs_n($got - $expected) <= $tol;
+    ok(?$test, $descr);
+    unless $test {
+        say("#got:      $got");
+        say("#expected: $expected");
+    }
+    ?$test;
+}
+
+is_approx(nqp::log_n(5), $log_5, 'got the log of 5');
+is_approx(nqp::log_n(0.1), $log_one_tenth, 'got the log of 0.1');