diff --git a/test/CachingTest.php b/test/CachingTest.php
index 1c48437..26da98b 100644
--- a/test/CachingTest.php
+++ b/test/CachingTest.php
@@ -227,7 +227,7 @@ public function test_expired_podcast_is_regenerated(): void
         $new_mtime = filemtime($cached_output_files[0]);
         
         // cache file should be refreshed
-        $this->assertNotEquals($old_mtime, $new_mtime);
+        $this->assertGreaterThan($old_mtime, $new_mtime);
     }
 
     public function test_too_new_file_not_included_in_podcast(): void
@@ -258,72 +258,12 @@ public function test_too_new_file_not_included_in_podcast(): void
         $new_mtime = filemtime($cached_output_files[0]);
 
         // cache file should be refreshed
-        $this->assertNotEquals($old_mtime, $new_mtime);
-    }
-
-    public function test_update_to_dir2cast_php_invalidates_cache(): void
-    {
-        file_put_contents('empty.mp3', 'test');
-
-        $source_file = readlink('dir2cast.php');
-        unlink('dir2cast.php');
-        copy($source_file, 'dir2cast.php');
-
-        age_dir_by('.', 86400);
-
-        $cached_output_files = glob('./temp/*.xml');
-
-        touch('dir2cast.php', time()-3600); // older than the minimum cache time, but newer than the cache files
-
-        clearstatcache();
-        $old_mtime = filemtime($cached_output_files[0]);
-
-        exec('php dir2cast.php --output=out.xml --dont-uncache --min-file-age=30');
-        $new_content = file_get_contents($this->file); // should have empty.mp3
-        $this->assertNotEquals($this->content, $new_content);
-        $this->assertEquals(1, preg_match('/empty\.mp3/', $new_content));
-
-        clearstatcache();
-        $cached_output_files = glob('./temp/*.xml');
-        $new_mtime = filemtime($cached_output_files[0]);
-
-        // cache file should be refreshed
-        $this->assertNotEquals($old_mtime, $new_mtime);
-    }
-
-    public function test_update_to_dir2cast_ini_invalidates_cache(): void
-    {
-        file_put_contents('empty.mp3', 'test');
-
-        $source_file = readlink('dir2cast.php');
-        unlink('dir2cast.php');
-        copy($source_file, 'dir2cast.php');
-        copy('../../dir2cast.ini', 'dir2cast.ini');
-
-        age_dir_by('.', 86400);
-
-        $cached_output_files = glob('./temp/*.xml');
-
-        touch('dir2cast.ini', time()-3600); // older than the minimum cache time, but newer than the cache files
-
-        clearstatcache();
-        $old_mtime = filemtime($cached_output_files[0]);
-
-        exec('php dir2cast.php --output=out.xml --dont-uncache --min-file-age=30');
-        $new_content = file_get_contents($this->file); // should have empty.mp3
-        $this->assertNotEquals($this->content, $new_content);
-        $this->assertEquals(1, preg_match('/empty\.mp3/', $new_content));
-
-        clearstatcache();
-        $cached_output_files = glob('./temp/*.xml');
-        $new_mtime = filemtime($cached_output_files[0]);
-
-        // cache file should be refreshed
-        $this->assertNotEquals($old_mtime, $new_mtime);
+        $this->assertGreaterThan($old_mtime, $new_mtime);
     }
 
     public function tearDown(): void
     {
+        unlink($this->file);
         chdir('..');
     }
 }
diff --git a/test/Caching_updates_to_dir2castTest.php b/test/Caching_updates_to_dir2castTest.php
new file mode 100644
index 0000000..f052351
--- /dev/null
+++ b/test/Caching_updates_to_dir2castTest.php
@@ -0,0 +1,103 @@
+<?php declare(strict_types=1);
+
+use PHPUnit\Framework\TestCase;
+
+class Caching_updates_to_dir2castTest extends TestCase
+{
+    public $file = 'out.xml';
+    public $output = '';
+    public $returncode = 0;
+
+    public $content = '';
+
+    public function setUp(): void
+    {
+        prepare_testing_dir();
+
+        if(is_link('dir2cast.php')) {
+            // replace symlink with a real file for this test, if it isn't already.
+            // It will generally be a symlink if we're doing code coverage (i.e. not on Windows)
+            $source_file = readlink('dir2cast.php');
+            unlink('dir2cast.php');
+            copy($source_file, 'dir2cast.php');
+        }
+
+        if(file_exists('dir2cast.ini')) {
+            // interferes with this test.
+            unlink('dir2cast.ini');
+        }
+
+        exec('php dir2cast.php --output=out.xml --dont-uncache --ignore-dir2cast-mtime', $this->output, $this->returncode);
+        $this->content = file_get_contents($this->file);
+
+        age_dir_by('.', 86400);
+    }
+
+    public function test_update_to_dir2cast_php_invalidates_cache(): void
+    {
+        file_put_contents('empty.mp3', 'test');
+
+        $cached_output_files = glob('./temp/*.xml');
+
+        touch('dir2cast.php', time()-3600); // older than the minimum cache time, but newer than the cache files
+
+        clearstatcache();
+        $old_mtime = filemtime($cached_output_files[0]);
+
+        sleep(1);
+        exec('php dir2cast.php --output=out.xml --dont-uncache --min-file-age=30 --debug', $debug_out);
+        // print(implode("\n", $debug_out));
+
+        // passthru('ls -laR');
+
+        clearstatcache();
+        $cached_output_files = glob('./temp/*.xml');
+        $new_mtime = filemtime($cached_output_files[0]);
+
+        // cache file should be refreshed
+        $this->assertGreaterThan($old_mtime, $new_mtime);
+
+        $new_content = file_get_contents($this->file);
+        $this->assertNotEquals($this->content, $new_content);
+
+        // empty.mp3 still too new
+        $this->assertEquals(0, preg_match('/empty\.mp3/', $new_content));
+    }
+
+    public function test_update_to_dir2cast_ini_invalidates_cache(): void
+    {
+        file_put_contents('empty.mp3', 'test');
+
+        copy('../../dir2cast.ini', 'dir2cast.ini');
+
+        $cached_output_files = glob('./temp/*.xml');
+
+        touch('dir2cast.ini', time()-3600); // older than the minimum cache time, but newer than the cache files
+
+        clearstatcache();
+        $old_mtime = filemtime($cached_output_files[0]);
+
+        sleep(1);
+        exec('php dir2cast.php --output=out.xml --dont-uncache --min-file-age=30 --debug', $debug_out);
+        // print(implode("\n", $debug_out));
+
+        clearstatcache();
+        $cached_output_files = glob('./temp/*.xml');
+        $new_mtime = filemtime($cached_output_files[0]);
+
+        // cache file should be refreshed
+        $this->assertGreaterThan($old_mtime, $new_mtime);
+
+        $new_content = file_get_contents($this->file);
+        $this->assertNotEquals($this->content, $new_content);
+
+        // empty.mp3 still too new
+        $this->assertEquals(0, preg_match('/empty\.mp3/', $new_content));
+    }
+
+    public function tearDown(): void
+    {
+        unlink($this->file);
+        chdir('..');
+    }
+}
diff --git a/test/Caching_updates_to_dir2cast_prepopulatedTest.php b/test/Caching_updates_to_dir2cast_prepopulatedTest.php
new file mode 100644
index 0000000..31035b0
--- /dev/null
+++ b/test/Caching_updates_to_dir2cast_prepopulatedTest.php
@@ -0,0 +1,37 @@
+<?php declare(strict_types=1);
+
+use PHPUnit\Framework\TestCase;
+
+class Caching_updates_to_dir2cast_prepopulatedTest extends Caching_updates_to_dir2castTest
+{
+    public function setUp(): void
+    {
+        prepare_testing_dir();
+        file_put_contents('pre-existing.mp3', 'test');
+        touch('pre-existing.mp3', time()-86400);
+
+        if(is_link('dir2cast.php')) {
+            // replace symlink with a real file for this test, if it isn't already.
+            // It will generally be a symlink if we're doing code coverage (i.e. not on Windows)
+            $source_file = readlink('dir2cast.php');
+            unlink('dir2cast.php');
+            copy($source_file, 'dir2cast.php');
+        }
+
+        if(file_exists('dir2cast.ini')) {
+            // interferes with this test.
+            unlink('dir2cast.ini');
+        }
+
+        exec('php dir2cast.php --output=out.xml --dont-uncache --ignore-dir2cast-mtime', $this->output, $this->returncode);
+        $this->content = file_get_contents($this->file);
+
+        age_dir_by('.', 86400);
+    }
+
+    public function tearDown(): void
+    {
+        $this->assertEquals(1, preg_match('/pre-existing\.mp3/', file_get_contents($this->file)));
+        parent::tearDown();
+    }
+}