  BOUT++ is a software package designed for solving plasma fluid models. It has
been used to simulate a wide range of plasma phenomena ranging from linear
stability analysis to 3D plasma turbulence, and is capable of simulating a wide
range of drift-reduced plasma fluid and gyro-fluid models. A verification
exercise has been performed as part of a EUROfusion Enabling Research project,
to rigorously test the correctness of the algorithms implemented in BOUT++, by
testing order-of-accuracy convergence rates using the Method of Manufactured
Solutions (MMS). We present tests of individual components including
time-integration and advection schemes, non-orthogonal coordinate systems and
the shifted metric procedure which is used to handle highly sheared grids. The
Flux Coordinate Independent (FCI) approach to differencing along magnetic
field-lines has been implemented in BOUT++, and is here verified using the MMS
in a sheared slab configuration. Finally we show tests of three complete
models: 2-field Hasegawa-Wakatani, 3-field reduced MHD in 3D toroidal
coordinates, and 5-field reduced MHD in slab geometry.
