Vulkan Push Constants never assigned or updated

I have been reading through Sascha Willem's example on push constants here and have attempted to implement them myself.

Oddly the VkPhysicalDeviceProperties.limits.maxPushConstantsSize is 1437341456 bytes which makes me think something else is very wrong. After rechecking it is showing as a more realistic value of 256 (I assume I did something incorrectly previously)

In my test project I have uniform buffers working, and I then started to tinker with push constants which will hopefully explain the inbetween state of my vertex shader

Here are some details of what I implemented: From what I understand, on creating a pipeline layout I need to specify the push constant ranges, which I do like so:

VkPushConstantRange pushConstantRange {};
pushConstantRange.stageFlags = VK_SHADER_STAGE_VERTEX_BIT;
pushConstantRange.offset = 0;
pushConstantRange.size = sizeof(ObjectPushConstantData);

And I add the push constant ranges to the pipeline layout CI like so:

pipelineLayoutInfo.pushConstantRangeCount = 1;
pipelineLayoutInfo.pPushConstantRanges = &pushConstantRange;

When creating my command buffers, I'm calling vkCmdPushConstants before drawing like so:

vkCmdPushConstants(this->commandBuffers[i], this->pipelineLayout, VK_SHADER_STAGE_VERTEX_BIT, 0, static_cast<uint32_t>(sizeof(ObjectPushConstantData)), &testObject);
vkCmdDrawIndexed(this->commandBuffers[i], static_cast<uint32_t>(indices.size()), 1, 0, 0, 0);
   

The type ObjectPushConstantData looks like so:

struct ObjectPushConstantData {
    glm::vec3 position;
    glm::vec3 rotation;
};

My vertex shader looks like this:

#version 450
#extension GL_ARB_separate_shader_objects : enable

layout(binding = 0) uniform UniformBufferObject {
    mat4 model;
    mat4 view;
    mat4 proj;
} ubo;

layout(location = 0) in vec3 inPosition;
layout(location = 1) in vec3 inColor;

layout(push_constant) uniform PushConsts {
    vec3 position;
    vec3 rotation;
} pushConsts;

layout(location = 0) out vec3 fragColor;

void main() {
    gl_Position = ubo.proj * ubo.view * ubo.model * vec4(pushConsts.position, 1.0);
    fragColor = inColor;
}