[tests] add a smoke test for System.IO.Directory (#10331)

Context: #10330

The problem fixed in #10330 makes me think we are missing a test.

And indeed, this crashed on CoreCLR!

    07-23 22:46:43.058  7510  7535 I NUnit   : DirectoryTest
    07-23 22:46:43.058  7510  7535 I NUnit   : GetFiles 
    07-23 22:46:43.061  7510  7535 D monodroid-assembly: [precompiled] clr_pinvoke_override ("libSystem.Native", "SystemNative_Stat")
    07-23 22:46:43.062  7510  7535 D monodroid: [precompiled] p/invoke found
    07-23 22:46:43.070  7510  7534 I droid.NET_Test: Explicit concurrent copying GC freed 45(32KB) AllocSpace objects, 0(0B) LOS objects, 57% free, 1148KB/2684KB, paused 1.838ms total 7.423ms
    07-23 22:46:43.072  7510  7535 D monodroid-assembly: [precompiled] clr_pinvoke_override ("libSystem.Native", "SystemNative_OpenDir")
    07-23 22:46:43.072  7510  7535 D monodroid: [precompiled] p/invoke found
    07-23 22:46:43.072  7510  7535 D monodroid-assembly: [precompiled] clr_pinvoke_override ("libSystem.Native", "SystemNative_ReadDir")
    07-23 22:46:43.072  7510  7535 D monodroid-assembly: Symbol 'SystemNative_ReadDir' in library 'libSystem.Native' not found in the generated tables, falling back to slow path
    07-23 22:46:43.072  7510  7535 F monodroid-assembly: Missing pinvoke [email protected]
    07-23 22:46:43.072  7510  7535 F monodroid-assembly: Abort at precompiled.cc:88:3 ('static void *xamarin::android::PinvokeOverride::monodroid_pinvoke_override(const char *, const char *)')
    --------- beginning of crash
    07-23 22:46:43.073  7510  7535 F libc    : Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 7535 (Instrumentation), pid 7510 (droid.NET_Tests)
    07-23 22:46:43.094  7550  7550 I crash_dump64: obtaining output fd from tombstoned, type: kDebuggerdTombstone
    07-23 22:46:43.095  1870  1870 I /system/bin/tombstoned: received crash request for pid 7535
    07-23 22:46:43.096  7550  7550 I crash_dump64: performing dump of process 7510 (target tid = 7535)
    07-23 22:46:43.099  7550  7550 F DEBUG   : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
    07-23 22:46:43.099  7550  7550 F DEBUG   : Build fingerprint: 'Android/sdk_phone_x86_64/generic_x86_64:10/QSR1.210820.001/7663313:userdebug/test-keys'
    07-23 22:46:43.099  7550  7550 F DEBUG   : Revision: '0'
    07-23 22:46:43.099  7550  7550 F DEBUG   : ABI: 'x86_64'
    07-23 22:46:43.100  7550  7550 F DEBUG   : Timestamp: 2025-07-23 22:46:43+0000
    07-23 22:46:43.100  7550  7550 F DEBUG   : pid: 7510, tid: 7535, name: Instrumentation  >>> Mono.Android.NET_Tests <<<
    07-23 22:46:43.100  7550  7550 F DEBUG   : uid: 10119
    07-23 22:46:43.100  7550  7550 F DEBUG   : signal 6 (SIGABRT), code -1 (SI_QUEUE), fault addr --------
    07-23 22:46:43.100  7550  7550 F DEBUG   : Abort message: 'Missing pinvoke [email protected]'
    07-23 22:46:43.100  7550  7550 F DEBUG   :     rax 0000000000000000  rbx 0000000000001d56  rcx 000078b597d263f8  rdx 0000000000000006
    07-23 22:46:43.100  7550  7550 F DEBUG   :     r8  000078b50724aa40  r9  0000000000000000  r10 000078b4b9e158d0  r11 0000000000000246
    07-23 22:46:43.100  7550  7550 F DEBUG   :     r12 000078b507358b00  r13 000078b4b9e159c0  r14 000078b4b9e15958  r15 0000000000001d6f
    07-23 22:46:43.100  7550  7550 F DEBUG   :     rdi 0000000000001d56  rsi 0000000000001d6f
    07-23 22:46:43.100  7550  7550 F DEBUG   :     rbp 000078b4b9e15a70  rsp 000078b4b9e158c8  rip 000078b597d263f8
    07-23 22:46:43.263  7550  7550 F DEBUG   : 
    07-23 22:46:43.263  7550  7550 F DEBUG   : backtrace:
    07-23 22:46:43.263  7550  7550 F DEBUG   :       #00 pc 00000000000943f8  /apex/com.android.runtime/lib64/bionic/libc.so (syscall+24) (BuildId: b5c6019a3b4ea61b5e9a2f56319b584e)
    07-23 22:46:43.263  7550  7550 F DEBUG   :       #1 pc 0000000000097146  /apex/com.android.runtime/lib64/bionic/libc.so (abort+182) (BuildId: b5c6019a3b4ea61b5e9a2f56319b584e)
    07-23 22:46:43.263  7550  7550 F DEBUG   :       #2 pc 00000000000c41c9  /data/app/Mono.Android.NET_Tests-3-1TDlT55wuyU7WHXRhzQQ==/split_config.x86_64.apk!libnet-android.release.so (offset 0x1850000) (xamarin::android::Helpers::abort_application(_LogCategories, char const*, bool, std::__ndk1::source_location)+425) (BuildId: f25730a1c837257e71f58c776b710328f9824f26)
    07-23 22:46:43.263  7550  7550 F DEBUG   :       #3 pc 00000000000cee85  /data/app/Mono.Android.NET_Tests-3-1TDlT55wuyU7WHXRhzQQ==/split_config.x86_64.apk!libnet-android.release.so (offset 0x1850000) (xamarin::android::PinvokeOverride::monodroid_pinvoke_override(char const*, char const*)+8725) (BuildId: f25730a1c837257e71f58c776b710328f9824f26)
    07-23 22:46:43.264  7550  7550 F DEBUG   :       #4 pc 00000000000cf191  /data/app/Mono.Android.NET_Tests-3-1TDlT55wuyU7WHXRhzQQ==/split_config.x86_64.apk!libnet-android.release.so (offset 0x1850000) (xamarin::android::Host::clr_pinvoke_override(char const*, char const*)+225) (BuildId: f25730a1c837257e71f58c776b710328f9824f26)
    07-23 22:46:43.264  7550  7550 F DEBUG   :       #5 pc 00000000003f21f6  /data/app/Mono.Android.NET_Tests-3-1TDlT55wuyU7WHXRhzQQ==/split_config.x86_64.apk

With the fix in place in #10330, it passes.

Author: jonathanpeppers

tests/Mono.Android-Tests/Mono.Android-Tests/Mono.Android.NET-Tests.csproj

@@ -104,6 +104,7 @@
     <Compile Include="System\ExceptionTest.cs" />
     <Compile Include="System\TimeZoneTest.cs" />
     <Compile Include="System.Drawing\TypeConverterTest.cs" />
+    <Compile Include="System.IO\DirectoryTest.cs" />
     <Compile Include="System.IO\DriveInfoTest.cs" />
     <Compile Include="System.IO.Compression\GZipStreamTest.cs" />
     <Compile Include="System.Linq\LinqExpressionTest.cs" />

tests/Mono.Android-Tests/Mono.Android-Tests/System.IO/DirectoryTest.cs

@@ -0,0 +1,25 @@
+using System;
+using System.IO;
+
+using NUnit.Framework;
+
+namespace System.IOTests;
+
+[TestFixture]
+public class DirectoryTest
+{
+	[Test]
+	public void GetFiles ()
+	{
+		var directory = Environment.GetFolderPath (Environment.SpecialFolder.UserProfile);
+		Assert.IsTrue (Directory.Exists (directory), "Directory does not exist: " + directory);
+
+		// Write a file
+		File.WriteAllText (Path.Combine (directory, "testfile.txt"), "This is a test file.");
+
+		// Verify that GetFiles returns the file
+		string [] files = Directory.GetFiles (directory);
+		Assert.IsNotNull (files, "GetFiles returned null for directory: " + directory);
+		Assert.IsTrue (files.Length > 0, "No files found in directory: " + directory);
+	}
+}