using Oceananigans
grid = RectilinearGrid(size=(4, 4, 4), extent=(1, 1, 1))
c = CenterField(grid)
c ≈ Oceananigans.Fields.ConstantField(1)

ERROR: FieldError: type Oceananigans.Fields.ConstantField has no field `grid`, available fields: `constant`
Stacktrace:
 [1] getproperty
   @ ./Base_compiler.jl:54 [inlined]
 [2] norm(a::Oceananigans.Fields.ConstantField{Int64, 3}; condition::Nothing)
   @ Oceananigans.Fields ~/Projects/Oceananigans.jl/src/Fields/field.jl:647
 [3] norm(a::Oceananigans.Fields.ConstantField{Int64, 3})
   @ Oceananigans.Fields ~/Projects/Oceananigans.jl/src/Fields/field.jl:646
 [4] isapprox(x::Field{Center, Center, Center, Nothing, RectilinearGrid{…}, Tuple{…}, OffsetArrays.OffsetArray{…}, Float64, FieldBoundaryConditions{…}, Nothing, Nothing}, y::Oceananigans.Fields.ConstantField{Int64, 3}; atol::Int64, rtol::Float64, nans::Bool, norm::typeof(LinearAlgebra.norm))
   @ LinearAlgebra ~/.julia/juliaup/julia-1.12.1+0.aarch64.apple.darwin14/share/julia/stdlib/v1.12/LinearAlgebra/src/generic.jl:1984
 [5] isapprox(x::Field{Center, Center, Center, Nothing, RectilinearGrid{…}, Tuple{…}, OffsetArrays.OffsetArray{…}, Float64, FieldBoundaryConditions{…}, Nothing, Nothing}, y::Oceananigans.Fields.ConstantField{Int64, 3})
   @ LinearAlgebra ~/.julia/juliaup/julia-1.12.1+0.aarch64.apple.darwin14/share/julia/stdlib/v1.12/LinearAlgebra/src/generic.jl:1978
 [6] top-level scope
   @ REPL[5]:1
Some type information was truncated. Use `show(err)` to see complete types.