diff --git a/test/AddrTest/AddrTest.php b/test/AddrTest/AddrTest.php
index 4cc8b78..35ce5af 100644
--- a/test/AddrTest/AddrTest.php
+++ b/test/AddrTest/AddrTest.php
@@ -121,4 +121,90 @@ class AddrTest extends \PHPUnit_Framework_TestCase
             "At least one of the name lookups did not resolve."
         );
     }
+
+
+    /**
+     * Check that caches do actually cache results.
+     */
+    function testCachingOfResults() {
+
+        $memoryCache = new MemoryCache();
+
+        $namesFirstRun = [
+            'google.com',
+            'github.com',
+            'google.com',
+            'github.com',
+        ];
+        
+        $namesSecondRun = [
+            'google.com',
+            'github.com',
+        ];
+
+        $setCount = count(array_unique(array_merge($namesFirstRun, $namesSecondRun)));
+        $getCount = count($namesFirstRun) + count($namesSecondRun);
+        
+        $mockedCache = \Mockery::mock($memoryCache);
+
+        /** @var  $mockedCache \Mockery\Mock */
+        
+        $mockedCache->shouldReceive('store')->times($setCount)->passthru();
+        $mockedCache->shouldReceive('get')->times($getCount)->passthru();
+
+        $mockedCache->makePartial();
+
+        $reactor = (new ReactorFactory)->select();
+        $resolver = (new ResolverFactory)->createResolver(
+            $reactor,
+            null, //$serverAddr = null,
+            null, //$serverPort = null,
+            null, //$requestTimeout = null,
+            $mockedCache,
+            null //$hostsFilePath = null
+        );
+
+        $results = [];
+        
+        //Lookup the first set of names
+        foreach ($namesFirstRun as $name) {
+            $resolver->resolve($name, function($addr) use($name, $resolver, &$results) {
+                    $results[] = [$name, $addr];
+                });
+        }
+
+        $reactor->run();
+
+        $this->assertCount(
+            count($namesFirstRun),
+            $results,
+            "At least one of the name lookups did not resolve in the first run."
+        );
+
+        $results = [];
+
+        //Lookup a second set of names
+        foreach ($namesSecondRun as $name) {
+            $resolver->resolve($name, function($addr) use($name, $resolver, &$results) {
+                    $results[] = [$name, $addr];
+                });
+        }
+
+        $reactor->run();
+
+        foreach ($results as $nameAndAddr) {
+            list($name, $addr) = $nameAndAddr;
+            $validIP = filter_var($addr, FILTER_VALIDATE_IP);
+            $this->assertNotFalse(
+                $validIP,
+                "Server name $name did not resolve to a valid IP address"
+            );
+        }
+
+        $this->assertCount(
+            count($namesSecondRun),
+            $results,
+            "At least one of the name lookups did not resolve in the second run."
+        );
+    }
 }
diff --git a/test/AddrTest/CacheTest.php b/test/AddrTest/CacheTest.php
index d4c02a5..65f5fc5 100644
--- a/test/AddrTest/CacheTest.php
+++ b/test/AddrTest/CacheTest.php
@@ -171,8 +171,5 @@ class CacheTest extends \PHPUnit_Framework_TestCase
 
         //check that garbage collection collects.
         $memoryCache->store($key, $value, 0);
-        $memoryCache->collectGarbage();
-
-        //TODO - check that the memoryCache contains a single item
     }
 }
diff --git a/test/AddrTest/HostsFileTest.php b/test/AddrTest/HostsFileTest.php
new file mode 100644
index 0000000..276838e
--- /dev/null
+++ b/test/AddrTest/HostsFileTest.php
@@ -0,0 +1,95 @@
+<?php
+
+use Addr\HostsFile;
+use Addr\NameValidator;
+use Addr\AddressModes;
+
+/**
+ * Class HostsFileTest
+ * @group hosts
+ */
+class HostsFileTest extends \PHPUnit_Framework_TestCase {
+
+    function testBasicIPV4() {
+        $tests = [
+            ['192.168.1.1', 'host1.example.com', AddressModes::INET4_ADDR, AddressModes::INET4_ADDR],
+            ['192.168.1.1', 'host2.example.com', AddressModes::INET4_ADDR, AddressModes::INET4_ADDR],
+
+            //Check that ipv4 is returned when prefer_inet6 is set
+            ['192.168.1.1', 'host1.example.com', AddressModes::PREFER_INET6, AddressModes::INET4_ADDR],
+
+            //Check non-existant domains return null
+            [null, 'host4.example.com', AddressModes::INET4_ADDR, null],
+        ];
+        
+        $this->runHostsFileTests($tests, __DIR__.'/../fixtures/ipv4Hosts.txt');
+    }
+
+
+    function testBasicIPV6() {
+        $tests = [
+            //Examples taken from http://en.wikipedia.org/wiki/IPv6_address
+            ['2001:db8::2:1', 'host1.example.com', AddressModes::INET6_ADDR, AddressModes::INET6_ADDR],
+            ['2001:db8:0:1:1:1:1:1', 'host2.example.com', AddressModes::INET6_ADDR, AddressModes::INET6_ADDR],
+            ['2001:db8::1:0:0:1', 'host3.example.com', AddressModes::INET6_ADDR, AddressModes::INET6_ADDR],
+
+            //Check that prefer inet6 does indeed return an inet6 address
+            ['2001:db8::2:1', 'host1.example.com', AddressModes::PREFER_INET6, AddressModes::INET6_ADDR],
+            
+            //Check request for ipv4 returns null
+            [null, 'host1.example.com', AddressModes::INET4_ADDR, null],
+        ];
+
+        $this->runHostsFileTests($tests, __DIR__.'/../fixtures/ipv6Hosts.txt');
+    }
+
+    function testMixedIPVersions() {
+        $tests = [
+            //Examples taken from http://en.wikipedia.org/wiki/IPv6_address
+            ['2001:db8::2:1', 'host1.example.com', AddressModes::INET6_ADDR, AddressModes::INET6_ADDR],
+            ['2001:db8:0:1:1:1:1:1', 'host2.example.com', AddressModes::INET6_ADDR, AddressModes::INET6_ADDR],
+            ['2001:db8::1:0:0:1', 'host3.example.com', AddressModes::INET6_ADDR, AddressModes::INET6_ADDR],
+            ['192.168.1.1', 'host1.example.com', AddressModes::INET4_ADDR, AddressModes::INET4_ADDR],
+            ['192.168.1.1', 'host2.example.com', AddressModes::INET4_ADDR, AddressModes::INET4_ADDR],
+            
+            //Check that the prefer inet6 works
+            ['2001:db8::2:1', 'host1.example.com', AddressModes::PREFER_INET6, AddressModes::INET6_ADDR],
+            
+            //Check that a host that is only listed as ipv6 does not return a result for ipv4
+            [null, 'host1.example.com', AddressModes::INET4_ADDR, null],
+            
+        ];
+
+        $this->runHostsFileTests($tests, __DIR__.'/../fixtures/mixedVersionHosts.txt');
+    }
+    
+    
+    
+    function runHostsFileTests($tests, $hostsFile) {
+        $nameValidator = new NameValidator;
+        $hostsFile = new HostsFile($nameValidator, $hostsFile);
+
+        foreach ($tests as $test) {
+            list($expectedResult, $hostname, $inputAddrMode, $expectedAddrMode) = $test;
+
+            $result = $hostsFile->resolve($hostname, $inputAddrMode);
+
+            if ($expectedResult === null) {
+                $this->assertNull($result);
+            }
+            else {
+                list($resolvedAddr, $resolvedMode) = $result;
+                    $this->assertEquals(
+                        $expectedAddrMode,
+                        $resolvedMode
+                    );
+                
+                $this->assertEquals(
+                    $expectedResult,
+                    $resolvedAddr,
+                    "Failed to resolve $hostname from $expectedResult. Expected `$expectedResult` but got `$resolvedAddr`."
+                );
+            }
+        }
+    }
+}
diff --git a/test/fixtures/ipv4Hosts.txt b/test/fixtures/ipv4Hosts.txt
new file mode 100644
index 0000000..fa1f64d
--- /dev/null
+++ b/test/fixtures/ipv4Hosts.txt
@@ -0,0 +1,2 @@
+192.168.1.1             host1.example.com
+192.168.1.2             host2.example.com
\ No newline at end of file
diff --git a/test/fixtures/ipv6Hosts.txt b/test/fixtures/ipv6Hosts.txt
new file mode 100644
index 0000000..0e6c82c
--- /dev/null
+++ b/test/fixtures/ipv6Hosts.txt
@@ -0,0 +1,3 @@
+2001:db8::2:1           host1.example.com
+2001:db8:0:1:1:1:1:1    host2.example.com
+2001:db8::1:0:0:1       host3.example.com
diff --git a/test/fixtures/mixedVersionHosts.txt b/test/fixtures/mixedVersionHosts.txt
new file mode 100644
index 0000000..60a6cf6
--- /dev/null
+++ b/test/fixtures/mixedVersionHosts.txt
@@ -0,0 +1,13 @@
+192.168.1.1             host1.example.com
+192.168.1.2             host2.example.com
+2001:db8::2:1           host1.example.com
+2001:db8:0:1:1:1:1:1    host2.example.com
+2001:db8::1:0:0:1       host3.example.com
+
+#next line is empty for coverage
+
+//empty_line_for_coverage
+
+
+#next line has invalid address for coverage
+1.2.300       doesntexist.com
\ No newline at end of file