diff --git a/t/16-randomprime.t b/t/16-randomprime.t
index 07091f93..4498464f 100644
--- a/t/16-randomprime.t
+++ b/t/16-randomprime.t
@@ -73,7 +73,7 @@ my %range_edge_empty = (
   "3842610774 to 3842611108" => [],
 );
 
-plan tests => 13+1+1+1+1
+plan tests => 15+1+1+1+1
               + (1 * scalar (keys %range_edge_empty))
               + (3 * scalar (keys %range_edge))
               + (2 * scalar (keys %ranges))
@@ -85,8 +85,11 @@ plan tests => 13+1+1+1+1
               + 0;
 
 my $infinity = 20**20**20;
+my $superbig = 1000000003;
 my $nrandom_range_samples = $extra ? 1000 : 50;
 
+ok(!eval { random_prime(1); }, "random_prime(1)"); # Just for coverage
+ok(!eval { random_prime(2,1); }, "random_prime(2,1)"); # Just for coverage
 ok(!eval { random_prime(undef); }, "random_prime(undef)");
 ok(!eval { random_prime(-3); }, "random_prime(-3)");
 ok(!eval { random_prime("a"); }, "random_prime(a)");
diff --git a/t/52-primearray.t b/t/52-primearray.t
index 64fe106c..504c26c6 100644
--- a/t/52-primearray.t
+++ b/t/52-primearray.t
@@ -60,8 +60,20 @@ my %test_indices = (
 );
 
 
-plan tests => 3 + 2 + scalar(keys %test_indices) + 8;
+plan tests => 3 + 3 + 2 + scalar(keys %test_indices) + 8;
 
+my $stderr = '';
+
+{
+  local $SIG{__WARN__} = sub { $stderr = $_[0] };
+  my @primes;  tie @primes, 'Math::Prime::Util::PrimeArray';
+  eval { $primes[0] = 0; };
+  like( $stderr, qr/cannot write/, "Can't store in PrimeArray");
+  eval { delete $primes[0]; };
+  like( $stderr, qr/cannot write/, "Can't delete in PrimeArray");
+  ok( defined $primes[7777], "All are defined" );
+}
+  
 {
   my @primes;  tie @primes, 'Math::Prime::Util::PrimeArray';
   my (@order, @got, @exp);