Frequent 'No tests found' when sharding tests

[chrisbanes]

Description

When sharding tests I get frequent (and seemingly random) 'No tests found' errors which fail the build.

See this PR: google/accompanist#463 for an example.

Steps to Reproduce

I'm not 100% sure what the repro is. Having a small number of tests in the module seems to be the trigger.

I think this is because the library is relying on hashCode being uniformly random over a small data-set, which isn't the case. If the module only has ~5 tests, and I'm sharding over 3 runs, the chance of at least 1 shard having 0 tests is quite high.

Expected Results

Shards with no tests from a module don't fail the build.

Actual Results

com.android.build.gradle.internal.testing.ConnectedDevice > No tests found.[test(AVD) - 5.1.1] FAILED 
No tests found. This usually means that your test classes are not in the form that your test runner expects (e.g. don't inherit from TestCase or lack @Test annotations).

AndroidX Test and Android OS Versions

1.3.0

Link to a public git repo demonstrating the problem:

google/accompanist#463

[chrisbanes]

#264 looks similar

[brettchabot]

AJUR's algorithm is a fork of bazel's HashBackedStrategy. https://github.com/bazelbuild/bazel/blob/master/src/java_tools/junitrunner/java/com/google/testing/junit/runner/sharding/HashBackedShardingFilter.java

However, I notice that the bazel default is a RoundRobinStrategy
https://github.com/bazelbuild/bazel/blob/master/src/java_tools/junitrunner/java/com/google/testing/junit/runner/sharding/RoundRobinShardingFilter.java

I cannot remember why the hash-backed algorithm was chosen for AJUR - perhaps because it was simpler...?

Changing the sharding algorithm could be disruptive, but perhaps we could make it configurable like bazel...

[TWiStErRob]

I think the hash based was chosen because of its stability, or at least that's a good argument for it. Adding/removing/renaming a test doesn't affect all the shards only that one test (maybe) moves to another shard, the rest is exactly as is. While with the round robin, renaming a test would totally reassign shards. This type of stability is really good for reproducibility and debugging flakyness. +1 for custom sharding with some good built-in examples.

[Apetree100122]

package androidx.test.ui.app ;import android.app.Service;import android.content.Intent ;import android.content.res.Configuration;import android.graphics.Color;
import android.graphics.PixelFormat;import android.graphics.drawable.ColorDrawable;import android.graphics.drawable.Drawable;import android.os.Build;import android.os.IBinder;import android.util.Log;import android.view.Gravity;import android.view.MotionEvent;import android.view.View;import android.view.View.OnClickListener;import android.view.WindowManager;import android.view.WindowManager.LayoutParams;import android.widget.ImageView;/** * Will use WindowManager to create a chat head button on the screen./public class ChatHeadService extends Service {
private static final String TAG = "ChatHeadService";
private WindowManager windowManager;
private ImageView chatHeadButton;
private boolean isRedColor = true; @OverRide public void onConfigurationChanged(Configuration newConfig) {Log.i(TAG, "Destroying and re-creating the chat head because of a configuration changed: " + newConfig); destroyChatHead(); createChatHead(); } @OverRide public void onCreate() { super.onCreate(); createChatHead(); } private void createChatHead() {
// create a chat head button chatHeadButton = new ImageView(this);chatHeadButton.setId(R.id.chat_head_btn_id); setChatHeadColor(isRedColor);windowManager = (WindowManager) getSystemService(WINDOW_SERVICE); final LayoutParams layoutParams = new WindowManager.LayoutParams(LayoutParams.WRAP_CONTENT, // width LayoutParams.WRAP_CONTENT,
// height LayoutParams.TYPE_PHONE,
// type LayoutParams.FLAG_NOT_FOCUSABLE,
// flagsPixelFormat.TRANSLUCENT);
// formatlayoutParams.gravity = Gravity.BOTTOM;
// add the chat head to window manager windowManager.addView(chatHeadButton, layoutParams);
// for moving the button on touch and slide chatHeadButton.setOnTouchListener(new View.OnTouchListener() {
private int initialX;
private int initialY;
private float initialTouchY; @Overridepublic boolean onTouch(View v, MotionEvent event) {switch (event.getAction()) {case MotionEvent.ACTION_DOWN:initialX = layoutParams.x;initialY = layoutParams.initialTouchX = event.getRawX();Initial: TouchY = event.getRawY(); break;case MotionEvent.ACTION_UP:
if (Math.abs(event.getRawX() - initialTouchX) == 0
&

[Apetree100122]

$variable_name = value;

Loops

1. IF Family:
   If, If-else, Nested-Ifs are used when you want to perform a certain set of operations based on conditional expressions.

If
if(conditional-expression){
//code
}
If-else
if(conditional-expression){
//code if condition is true
} else {
//code if condition is false
}
Nested-If-else
if(condition-expression1) {
//code if above condition is true
} elseif(condition-expression2){
//code if above condition is true
}
elseif(condition-expression3) {
//code if above condition is true
}
...
else {
//code if all the conditions are false
}
2. Switch:
Switch is used to execute one set of statement from multiple conditions.

switch(conditional-expression) {
case value1:
// code if the above value is matched
break; // optional
case value2:
// code if the above value is matched
break; // optional
...

default:
// code to be executed when all the above cases are not matched;
}

3. For:
   For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){
// code
}
For-each:
// you can use any of the below syntax
foreach ($array as $element-value) {
//code
}

foreach ($array as $key => $element-value) {
//code
}
4. While:
While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {
// code
}
5. Do-While:
Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
// code
} while (condition);
Functions
Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

How to define a Function
function function_name(parameters) {
//code
}
How to call a Function
function_name (parameters)