Tests: Do not read system user's data

The tests would initialize Base, PreferencesData with default settings
and/or run the arduino executable, without specifying any settings to
use. In practice, this would read settings from e.g. `~/.arduino15`,
load libraries from the user's sketchbook, etc.

This is not a good idea, since this can be influence the test. For
example, the presence of invalid libraries would cause extra output to
be generated, which breaks the `--version` test. Or having the "Use
external editor" setting set would break tests that try to edit a
sketch.

This commit fixes this. The core of this commit is in
`AbstractWithPreferencesTest`, which sets up a clean settings dir (to
replace `~/.arduino15`) with a sketchbook and `preferences.txt` file
inside before every test (and removes it again after the test.

For some tests, this is enough, but some tests create an instance of
`Base`, which again initializes everything, including preferences, from
the default location. To prevent that, `--preferences-file` is passed to
the `Base` constructor, loading the previously set up preferences. This
is handled by the new `AbstractWithPreferencesTest.createBase()` method.

Furthermore, CommandLineTest calls the actual Arduino executable, which
has the same problem. This is fixed by passing the same
`--preferences-file` option on the commandline (generated by
`AbstractWithPreferencesTest.getBaseArgs()`).

This should prevent all tests from reading the the default settings
files, fixing some tests on my system and even speeding up the tests
somewhat (due less libraries and cores to load, probably).

app/test/processing/app/AbstractGUITest.java

@@ -60,7 +60,7 @@ public abstract class AbstractGUITest extends AbstractWithPreferencesTest {
     window = GuiActionRunner.execute(new GuiQuery<ArduinoFrameFixture>() {
       @Override
       protected ArduinoFrameFixture executeInEDT() throws Throwable {
-        return new ArduinoFrameFixture(new Base(new String[0]).editors.get(0));
+        return new ArduinoFrameFixture(createBase().editors.get(0));
       }
     });
   }

app/test/processing/app/AbstractWithPreferencesTest.java

@@ -29,6 +29,7 @@
 
 package processing.app;
 
+import static org.junit.Assert.assertEquals;
 import org.junit.Before;
 import org.junit.After;
 
@@ -47,12 +48,30 @@ public abstract class AbstractWithPreferencesTest {
    * Subclasses can add files here in @Test or @Before functions.
    */
   protected List<File> deleteAfter = new LinkedList<File>();
+  protected File preferencesFile;
 
   @Before
   public void init() throws Exception {
+    File settingsDir = Files.createTempDirectory("arduino_test_settings").toFile();
+    deleteAfter.add(settingsDir);
+
+    preferencesFile = new File(settingsDir, "preferences.txt");
+    File sketchbookDir = new File(settingsDir, "sketchbook");
+    sketchbookDir.mkdir();
+
     BaseNoGui.initPlatform();
     BaseNoGui.getPlatform().init();
-    PreferencesData.init(null);
+
+    PreferencesData.init(preferencesFile);
+    // Do not read anything from e.g. ~/.arduino15
+    PreferencesData.set("settings.path", settingsDir.toString());
+    // Do not read or write the default ~/Arduino sketchbook
+    PreferencesData.set("sketchbook.path", sketchbookDir.toString());
+    // Write the defaults, with these changes to file. This allows them
+    // to be reloaded when creating a Base instance (see getBaseArgs()
+    // below).
+    PreferencesData.save();
+
     Theme.init();
 
     BaseNoGui.initPackages();
@@ -61,6 +80,31 @@ public abstract class AbstractWithPreferencesTest {
     deleteAfter.add(Base.untitledFolder);
   }
 
+  /**
+   * Returns arguments to be passed to the Base constructor or on the
+   * commandline to set up the created dummy environment.
+   */
+  protected String[] getBaseArgs() {
+    return new String[] {
+      // Preferences are loaded (using --preferences-file) before
+      // processing any other commandline options (e.g. --pref), so only
+      // use --preferences-file here. Also, this does not affect the
+      // "action" mode, for tests that require the GUI to be loaded.
+      "--preferences-file", preferencesFile.toString(),
+    };
+  }
+
+  /**
+   * Creates a new instance of Base. Always use this rather than calling
+   * it directly, to ensure the right settings are used.
+   */
+  protected Base createBase() throws Exception {
+    Base base = new Base(getBaseArgs());
+    // Doublecheck that the right preferencesFile was loaded
+    assertEquals(preferencesFile, PreferencesData.preferencesFile);
+    return base;
+  }
+
   @After
   public void cleanup() throws IOException {
     for (File f : deleteAfter)

app/test/processing/app/CommandLineTest.java

@@ -45,7 +45,13 @@ import org.junit.Test;
 import processing.app.helpers.OSUtils;
 import processing.app.helpers.PreferencesMap;
 
-public class CommandLineTest {
+/**
+ * This extends AbstractWithPreferencesTest which initializes part of
+ * the internal Arduino structures. Most of that is not required, but it
+ * also conveniently sets up a settings directory and preferences file,
+ * which we can use here (through getBaseArgs()).
+ */
+public class CommandLineTest extends AbstractWithPreferencesTest {
 
   private static File buildPath;
   private static File arduinoPath;
@@ -81,6 +87,7 @@ public class CommandLineTest {
 
     List<String> args = new ArrayList<String>();
     args.add(arduinoPath.getAbsolutePath());
+    args.addAll(Arrays.asList(getBaseArgs()));
     args.addAll(Arrays.asList(extraArgs));
 
     System.out.println("Running: " + String.join(" ", args));

app/test/processing/app/DefaultTargetTest.java

@@ -57,7 +57,7 @@ public class DefaultTargetTest extends AbstractWithPreferencesTest {
     PreferencesData.set("board", "unreal_board");
 
     // should not raise an exception
-    new Base(new String[0]);
+    createBase();
 
     // skip test if no target platforms are available
     Assume.assumeNotNull(BaseNoGui.getTargetPlatform());