Data matching between 2 layers which do not overlap

I would like to know how a vector layer can takes attributes of a field, of another vector layer which is not overlapping.

For example, there are 2 vector layers, test_1 (2 records A,B) and test_2 (3 records 1,2,3), and i should have as output, the layer test_1 with the same route, but composed/separated by 3 records as test_2, with the additional field ID (1,2,3) moved to the attribute table of test_1.

This geometry process should be as precise as possible.
Any suggestions, QGIS geoprocessing tools?

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Thank You for the reply! Using “Join Attributes by Nearest” it doesn’t work because the records continue to begins and ends in the same points of Test_1. I should have Test_1 divided in 3 records, for example at the transects of Test_2; with 1,2,3 in the attribute table. Look at the pic.

I’m thinking to use this flow (“Transect” of Test_2 -> “Split by lines” of Test_1 from transect -> “Join Attributes by Nearest” -> “Group geometries” of Test_1 from ID), but this is not accurate when a meet an intersection of lines because the transects create much confusion. Thank you!