Added a small test for the render_3d output.

- I used it to reproduce the temporal project generation.

tests/test_plot/test_step.py

@@ -61,3 +61,12 @@ def test_step_variant_1(test_dir):
     # Check all outputs are there
     ctx.expect_out_file(prj+'-3D.step')
     ctx.clean_up(keep_project=True)
+
+
+def test_render_3d_variant_1(test_dir):
+    prj = 'kibom-variant_3'
+    ctx = context.TestContext(test_dir, 'test_render_3d_variant_1', prj, 'render_3d_variant_1', '')
+    ctx.run(extra_debug=True)
+    # Check all outputs are there
+    ctx.expect_out_file(prj+'-3D_top.png')
+    ctx.clean_up(keep_project=True)

tests/yaml_samples/render_3d_variant_1.kibot.yaml

@@ -0,0 +1,24 @@
+# Example KiBot config file
+kibot:
+  version: 1
+
+filters:
+  - name: '3D change'
+    comment: 'Changes R2 3D model'
+    type: var_rename
+    force_variant: 'default'
+
+variants:
+  - name: 'default'
+    comment: 'Default variant'
+    type: ibom
+    variants_blacklist: T2,T3
+    pre_transform: '3D change'
+
+outputs:
+  - name: '3d_default'
+    comment: "3D view w/variant"
+    type: render_3d
+    options:
+      variant: default
+