ithout enabling the extension`);
        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no more errors");
        gl.texParameterf(gl.TEXTURE_2D, gl[pname], MIRROR_CLAMP_TO_EDGE_EXT);
        wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, `value unknown for ${pname} via texParameterf without enabling the extension`);
        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no more errors");
    }

    if (!gl.createSampler) return;

    const sampler = gl.createSampler();
    for (const pname of pnames) {
       