Testing/Conformance

Conformance tests

In order for an implementation to claim it supports WebGL it must pass a set of conformance tests. Many of the tests are there to hopefully find incompatibilites between implementations. This is to promote the goal that a WebGL program created in a particular browser on a particular OS will run on any browser and any OS without modification.

The biggest issue is that WebGL is based on OpenGL ES 2.0 which has significant differences from desktop OpenGL. Those differences need to be tested against.

Note: As for this writing these tests have not been implemented. If you are interested in implementing them please speak up.

Current test suite

The currently available tests are hosted at

   https://cvs.khronos.org/svn/repos/registry/trunk/public/webgl/sdk/tests/
   https://cvs.khronos.org/svn/repos/registry/trunk/public/webgl/sdk/tests/fast/

Their source code can be checked out with

   svn checkout https://cvs.khronos.org/svn/repos/registry/trunk/public/webgl

More work is needed on these tests, for example to write a harness which runs all of them and verifies against expected results. Contributions are welcome.

Tests

Below is a non-exhaustive list of tests an implementation must pass.

• Test that glDrawElements fails if an index is out of range for the currently bound buffers.

• Test that glDrawElements succeeds if asked to draw a subset of some buffer that is in range for the subset of indices but would be out of range if the entire index buffer is used.

Example: An index buffer has the following indices [20, 30, 0, 1, 2, 3, 40, 50]. The bound buffers only have 4 vertices. If glDrawElements is called with count = 8, offset = 0 it should fail. If called with count = 4, offset = 2 it should succeed.

• Test that glDrawElements and glDrawArrays fails if any vertex attributes needed by the current program are enabled but not supplied.

• Test that glUniformMatrixfv fails if the transpose parameter is not GL_FALSE.

• Test that glTexImage2D fails if any Desktop GL enums are passed in, especially desktop only texture formats and source format enums

• Test that trying to set LEVEL > 0 on NPOT textures fails. GLES2 only supports NPOT textures with no mips.

• Test that drawing an NPOT with incorrect parameters sends 0,0,0,1 to the fragment shader. GLES2

• Test that glDrawElements fails with GL_INT

• Test that in general, any GLenum that is allowed on Deskop GL but not in GLES2 fails. There are lots of these.

• Test that calling glVertexAttribPointer when glBindBuffer's bound array buffer is 0 fails.

• Test that changing the size of the canvas does not change the size of the viewport.

• Test that shaders that use identifiers allowed in Desktop GL but not in GLES2 fail to compile.

 * for example, a shader with "uniform vec4 gl_world;" must return -1 when GetUniformLocation(prg, "gl_world") is called. (GLES forbids uniforms with the prefix "gl_")

• Test that in general, any thing allowed in GLSL on Desktop GL but not in GLES2 fails to compile.

• Test that shaders that use the "precision" keyword compile. (That keyword is not supported by desktop GL which means WebGL implementations will have to parse it out)

• Test that calling TexImage2D with border != 0 generates INVALID_VALUE

• Test that calling TexImage2D with no WebGLArray succeeds

• Test that calling TexImage2D with no WebGLArray that created texture's content is is 0,0,0,0. GL does not do this so WebGL implementations will need to otherwise it will be possible for WebGL to get the contents of vram from previously run apps.

• Test that shaders with something other than "#version 100" fail.

• Test that shaders with "#ifdef GL_ES" compile as though GL_ES is true. DesktopGL will not do this meaning conforming WebGL implementation will need to do their something to make this work.

• Test that shaders with "#extension" fail.