Add "Test example from AtomsBase.jl documentation" in test/AtomsBase.jl

test/AtomsBase.jl

@@ -0,0 +1,20 @@
+using AtomsBase
+using Unitful: ustrip, @u_str
+using UnitfulLinearAlgebra
+
+# See https://juliamolsim.github.io/AtomsBase.jl/stable/tutorial/#System-interface-and-conventions v0.3.5
+@testset "Test example from AtomsBase.jl documentation" begin
+    box = [[10.0, 0.0, 0.0], [0.0, 10.0, 0.0], [0.0, 0.0, 10.0]]u"Å"  # Note the unit!
+    bc = [Periodic(), Periodic(), Periodic()]
+    hydrogen = FlexibleSystem(
+        [Atom(:H, [0, 0, 1.0]u"bohr"), Atom(:H, [0, 0, 3.0]u"bohr")], box, bc
+    )
+    cell = Cell(
+        box, [[0, 0, ustrip(u"Å", 0.1u"bohr")], [0, 0, ustrip(u"Å", 0.3u"bohr")]], [:H, :H]
+    )
+    @test Cell(hydrogen) == cell
+    @test all(
+        position(FlexibleSystem(cell)) .≈
+        [uconvert.(u"Å", [0, 0, 1.0]u"bohr"), uconvert.(u"Å", [0, 0, 3.0]u"bohr")],
+    )
+end

test/runtests.jl

@@ -5,4 +5,5 @@ using Test
     # Write your tests here.
     include("lattice.jl")
     include("eachatom.jl")
+    include("AtomsBase.jl")
 end