iNaturalistReactNative/tests/unit/components/SharedComponents/Map/mapHelpers.test.js

import {
  getMapRegion,
  regionFromBounds,
} from "components/SharedComponents/Map/helpers/mapHelpers";

describe( "regionFromBounds", ( ) => {
  it( "covers exactly the bounds it was given", ( ) => {
    const region = regionFromBounds( {
      swlat: 10, swlng: 20, nelat: 30, nelng: 40,
    } );

    expect( region.latitude ).toBe( 20 );
    expect( region.longitude ).toBe( 30 );
    expect( region.latitudeDelta ).toBe( 20 );
    expect( region.longitudeDelta ).toBe( 20 );
  } );

  it( "round trips the bounds of a viewport without growing it", ( ) => {
    const bounds = {
      swlat: 37.7, swlng: -122.5, nelat: 37.8, nelng: -122.4,
    };
    const region = regionFromBounds( bounds );

    expect( region.latitude - ( region.latitudeDelta / 2 ) ).toBeCloseTo( bounds.swlat );
    expect( region.longitude - ( region.longitudeDelta / 2 ) ).toBeCloseTo( bounds.swlng );
    expect( region.latitude + ( region.latitudeDelta / 2 ) ).toBeCloseTo( bounds.nelat );
    expect( region.longitude + ( region.longitudeDelta / 2 ) ).toBeCloseTo( bounds.nelng );
  } );

  it( "keeps deltas positive when the bounds are inverted", ( ) => {
    const region = regionFromBounds( {
      swlat: 30, swlng: 40, nelat: 10, nelng: 20,
    } );

    expect( region.latitudeDelta ).toBe( 20 );
    expect( region.longitudeDelta ).toBe( 20 );
  } );
} );

describe( "getMapRegion", ( ) => {
  it( "frames the bounds with a bit of padding so the full range is visible", ( ) => {
    const region = getMapRegion( {
      swlat: 10, swlng: 20, nelat: 30, nelng: 40,
    } );

    expect( region.latitude ).toBe( 20 );
    expect( region.longitude ).toBe( 30 );
    expect( region.latitudeDelta ).toBe( 28 );
    expect( region.longitudeDelta ).toBe( 28 );
  } );

  it( "centers on the point when the bounds are a single point", ( ) => {
    const region = getMapRegion( {
      swlat: 37.5, swlng: -122.1, nelat: 37.5, nelng: -122.1,
    } );

    expect( region.latitude ).toBe( 37.5 );
    expect( region.longitude ).toBe( -122.1 );
    expect( region.latitudeDelta ).toBe( 0 );
    expect( region.longitudeDelta ).toBe( 0 );
  } );

  it( "pads the dimension that has range when the bounding box is flat", ( ) => {
    const region = getMapRegion( {
      swlat: 37.5, swlng: -122.5, nelat: 37.5, nelng: -120.5,
    } );

    expect( region.latitude ).toBe( 37.5 );
    expect( region.longitude ).toBe( -121.5 );
    expect( region.latitudeDelta ).toBe( 0 );
    expect( region.longitudeDelta ).toBeCloseTo( 2.8 );
  } );

  it( "does not ask for impossible deltas when the bounds are worldwide", ( ) => {
    const region = getMapRegion( {
      swlat: -90, swlng: -180, nelat: 90, nelng: 180,
    } );

    expect( region.latitude ).toBe( 0 );
    expect( region.longitude ).toBe( 0 );
    expect( region.latitudeDelta ).toBe( 89 );
    expect( region.longitudeDelta ).toBe( 179 );
  } );

  it( "keeps deltas positive when the bounds are inverted", ( ) => {
    const region = getMapRegion( {
      swlat: 30, swlng: 40, nelat: 10, nelng: 20,
    } );

    expect( region.latitudeDelta ).toBe( 28 );
    expect( region.longitudeDelta ).toBe( 28 );
  } );
} );